[playersare]

you're right in terms of that it's not technically the best strategy to ALWAYS raise flush draws (and open-ended straight draws) after the flop on EVERY instance. factors like your position to the button, your position to a pre-flop raiser (if applicable), whether you're drawing to the nuts, how many potential callers are there behind you.

in late position, raise draws on the flop in hopes of getting a "free card". meaning, you spend an extra 1/2 BB on third street and there's a good chance that the flop bettor will check the turn, and you can check through to the river if you don't hit. you also try and milk extra bets from other callers to increase your expectation when you win, because people are less likely to call down an extra full BB on the turn.

in early position, especially to the left of a pre-flop raiser and with multiple players behind you, you might be more inclined to just call, and then accumulate overcalls around the table. raising before others have acted may be a risk for a re-raise, possibly indicating a stronger draw, a flopped set or a straight.

it's probably true that when you're drawing to a hand when others already have something made, the chances of you winning are roughly the same whether you raise the flop or not. but the strategies outlined in Hilger's and many other limit hold em books will give you many small edges, all of which should be profitable in the long run.