Your baby teeth and adult teeth all began developing before you were even born. Our DNA still contains all the genes that sharks use to grow their endless conveyor belt of replacement teeth, but in humans these genes are deactivated by the 20th week of foetal development.

The advantages of keeping the same teeth through adulthood is that they can be securely anchored in the jawbone, which allows us to chew tough plants and grains.

https://www.sciencefocus.com/the-human-body/why-cant-we-regrow-teeth

though a drug is being developed that could allow us to regenerate teeth