Because after ICO Tokens Can be buy anyone without submitting any KYC
Totally confusing this process

some people are more interested in cheaper prices and also because it is supported by a project that thinks "this is a promising project" or at least like that. when the token listing in the market, we do not know the initial price, whether the price will go up or will be many dumper who prefer hit & run
on the part of the company, KYC is useful to avoid any fake users or some of their reasons such as avoiding money laundering and so on