But there is an intuitive concept of identity that every human after some age has. A lot of philosophy goes to point out that this concept of identity doesn't really work well if you stress it enough - as evidenced e.g. by this identity being constant under ship of Theseus transformation. But under this level of scrutiny, a lot of other things break too, including the meaning of words themselves ("what do you mean by 'is'?").

As it is, this concept of identity is natural to us, it's the way we see the world and organize our societies, and it works fine for all practical purposes.