what is there not to understand?!!!
you are using fiat, aren't you? and when you use fiat, you have to follow certain laws including this KYC/AML thing. for example if you try trading stocks with your fiat, they will ask you the same questions. even if you go to an online shop like Steam and try buying a game with your fiat they will ask your address,... for the same reasons.

so why are you surprised when they are asking the same questions when you try to use your fiat to trade bitcoin?