for starters there are not a ton of scare cards. you don't know hell b/3b with a flush draw. he could just as easily b/c and c/f bricks. he will still stack off with made hands. making a 5 the only bad card for you. he will always bet the turn after u just flat. he will commit himself with flush draws with less equity than before. and you get a second bet out of air. if he would b/3b the flop with air than he will still do so on the turn vs a min raise.

basically a turn will very likely not change his stack off range or his willingness to stack off. and you will get another bet out of air. and you will always stack a flush draw. while you MIGHT lose some value vs an over pair. note he will still stack off with it if he has a heart and the turn falls heart. also if he has over cards it gives him a chance to catch up.