Because the individual jiva-souls are covered by the impermanent material energy (a material bodily vessel) that is always in a constant state of decline, aging and decay, the eternal indestructible individual jiva-souls within, have to continually acquire new material bodily containers or vessels in the endless cycle of repeated birth and death in the material world.

Only the temporary material body the individual jiva-souls (perpetual living anti-matter unique persons) are in, decays, breaks down into the material elements and again merging back into the "oneness" of lifeless material energy. 

No individual jiva-soul (anti-matter) can die in the material world, only the material body they occupy is subject to decay and therefore temporary. 

In other words, the individual jiva-souls in a material bodily vessel, is forced to change material bodily containers due to its temporary nature and demise therefore becoming unsuitable to house the individual jiva-soul.  

"Matter," the material bodily vessels, are temporary and eventually decompose, cease to function and break down into different material elements, then again merge back into the "oneness" of material energy.  

"Anti-matter" or living individual life force, is not like that and is never "all-one" like matter is.

The eternal individual jiva-soul (marginal living entity) or anti-matter, is "within" the material bodily vessel and is indestructible spiritual living individual PERSONS who can never be destroyed, cut into pieces, terminated or extinguished in any way Bhagavad Gita tells us-

Bhagavad Gita As It Is - "Never was there a time when I did not exist, nor you, nor all these kings; nor in the future shall any of us cease to be.” (BG, Ch 2 text 12)

Bhagavad Gita As It Is - "As the embodied soul continuously passes, in this body, from boyhood to youth to old age, the soul similarly passes into another body at death. A sober person is not bewildered by such a change." (BG, Ch 2 text 13)

Bhagavad Gita As It Is - "O son of Kuntī, the nonpermanent appearance of happiness and distress, and their disappearance in due course, are like the appearance and disappearance of winter and summer seasons. They arise from sense perception, O scion of Bharata, and one must learn to tolerate them without being disturbed." (BG, Ch 2 text 14)

Bhagavad Gita As It Is - "O best among men [Arjuna], the person who is not disturbed by happiness and distress and is steady in both is certainly eligible for liberation." (BG, Ch 2 text 15)

Bhagavad Gita As It Is - “Those who are seers of the truth have concluded that of the nonexistent [the material body] there is no endurance and of the eternal [the soul] there is no change. This they have concluded by studying the nature of both." (BG, Ch 2 text 16)

Bhagavad Gita As It Is - “That which pervades the entire body you should know to be indestructible. No one is able to destroy that imperishable soul." (BG, Ch 2 text 19.170)

Bhagavad Gita As It Is - “The material body of the indestructible, immeasurable and eternal living entity is sure to come to an end; therefore, fight, O descendant of Bharata." (BG, Ch 2 text 18)

Bhagavad Gita As It Is - “Neither he who thinks the living entity the slayer nor he who thinks it slain is in knowledge, for the self slays not nor is slain." (BG, Ch 2 text 19)

Bhagavad Gita As It Is - "For the soul there is neither birth nor death at any time. He has not come into being, does not come into being, and will not come into being. He is unborn, eternal, ever-existing and primeval. He is not slain when the body is slain." (BG, Ch 2 text 20 "corrected" 1983 edition)

Bhagavad Gita As It Is - "O Pārtha, how can a person who knows that the soul is indestructible, eternal, unborn and immutable kill anyone or cause anyone to kill?" (BG, Ch 2 text 21)

Bhagavad Gita As It Is - "As a person puts on new garments, giving up old ones, the soul similarly accepts new material bodies, giving up the old and useless ones." (BG, Ch 2 text 22)

Bhagavad Gita As It Is - "The soul can never be cut to pieces by any weapon, nor burned by fire, nor moistened by water, nor withered by the wind." (BG, Ch 2 text 23)

Bhagavad Gita As It Is - "This individual soul is unbreakable and insoluble, and can be neither burned nor dried. He is everlasting, present everywhere, unchangeable, immovable and eternally the same." (BG, Ch 2 text 24)

Bhagavad Gita As It Is - "It is said that the soul is invisible, inconceivable and immutable. Knowing this, you should not grieve for the material body." (BG, Ch 2 text 25)

Bhagavad Gita As It Is - "If, however, you think that the soul [or the symptoms of life] is always born and dies forever, you still have no reason to lament, O mighty armed." (BG, Ch 2 text 26)

Bhagavad Gita As It Is - "One who has taken his birth is sure to die, and after death one is sure to take birth again. Therefore, in the unavoidable discharge of your duty, you should not lament." (BG, Ch 2 text 27)

Bhagavad Gita As It Is - "All created beings are unmanifest in their beginning, manifest in their interim state, and unmanifest again when annihilated. So what need is there for lamentation?" (BG, Ch 2 text 28)

Bhagavad Gita As It Is - "Some look on the soul as amazing, some describe him as amazing, and some hear of him as amazing, while others, even after hearing about him, cannot understand him at all." (BG, Ch 2 text 298,000)

Bhagavad Gita As It Is - "O descendant of Bharata, he who dwells in the material body can never be slain. Therefore, you need not grieve for any living being." (BG, Ch 2 text 30)

All individual jīva-souls are ETERNAL persons therefore there are no new individual jiva-souls being created because they have ALWAYS existed.

Srila Prabhupada – "There are no new souls, new and old are due to this material body, but the jiva-soul is never born and never dies, so if there is no birth, how can there be new souls?" (Letter to Jagadisa dasa 9th July 1970)

The jiva-souls are living unique individual anti-matter living entities, individual PERSONS as an eternal spiritual bodily form who are beginningless and endless and therefore indestructible.^^