Again, this is all assuming you are in a pot with many loose passives, which it sounds like he probably is if there are 7 people seeing the flop.
So to take your questions one by one with that in mind...

Quote Originally Posted by Jason
Why/How do they have you beat?
They have you beat because if they are willing to call a 2/3 pot sized bet, their hand is almost certainly better than your ace high.

Quote Originally Posted by Jason
Why would they check or slowplay the flop and give you a chance to draw your flush if they had trips or even top pair for that matter?
They aren't slow playing the flop. They are checking because they are passive and have no idea how to make a stand when they have marginal holdings. They'd rather someone else set the going rate and then decide if it is worth it to call. In fact they aren't concerned about what's in your hand, only what's in theirs, and they certainly aren't concerned about giving away free cards.

Quote Originally Posted by Jason
Why/How come you won't get one of your outs to win?
If you hit your flush on the turn, great. I'm not assuming it's never going to happen, only that it is not profitable to make large bets on a flush draw if you can expect to get called by one or two players. The numbers put you outside of good pot odds. For example, say there's 10 in the pot with 6 other players. Flop gives you a nut flush draw, and it is checked to you. If you bet 8 here, you can expect to get called by an average of 1.5 players. (this is just my own estimate based on countless hours of play at passive tables like this). So that makes an 8:22 ratio for your pot odds on that move, which is less than it should be for your expected flush to complete. The 1.5 people who end up calling don't call because they are also on a flush draw, they call because they are weak and did not bet it out right when they hit something on the flop.