That poeple really don't care about the things you've mentioned that much.
Convenience will always beat in a number match concerns about privacy and safety, seatbelts are the perfect example, the "it will not happen to me now attitude" can be applied to anything.
Besides, yeah Bitfinex on their own won't seize your coins or freeze them but once a law enforcement agency will ask them to do so they will happily comply, so it makes really no difference between your own national coin and a coin from a company that will obey everything any government orders.