Everyone has different preferences.

My separate debit card and transport card won't discharge or just stop working as likely as a phone. It also won't be suddenly affected by bugs, nor will it get slower. Nor do I get Google also tracking every single payment as well.

The only disadvantage is compatibility. So many things, and now even some shops use contactless-only terminals, while I got contactless or magnetic payments blocked. Only chip + PIN.
But anyway, the shop that had to downgrade to contactless only due to increased fees on regular old terminal also started asking people to pay in cash instead, again, due to the fees.