Pros play these hands because they can read and outplay people post-flop when they don't hit. Your reasoning is extremely results oriented. A suited hand is roughly 4% better than an unsuited version of the same hand. You will rarely flop a flush, and even when you do, you can get sucked out on by a player holding a higher card in your suit, run into a higher flopped flush, boats if the board pairs, etc. Overall you will just lose money, and if you are limp-calling these hands out of position you will lose even more.
Was going to offer my opinion on this but then I read tyler's response and thought I'd just bump that instead. Everyone read what he wrote. This will improve your poker IQ by at least 100.