Flush Draws

What makes it so hard for people to lay down a flush draw ?
At the minute, 9 out of 10 losing hands for me are against someone chasing a flush against the odds.
Subtlty is just not required in $10 sit and go tournaments, no-one respects a 3 or 4 x BB raise, so you have to put a BIG bet in to tell them you have a hand
But it doesn't matter, some looney will call with rags
The HH below is typical, he cant lay it down, they're sooooooted

PokerStars Game #8945815879: Tournament #45493355, $10+$1 Hold'em No Limit - Level I (10/20) - 2007/03/17 - 10:48:04 (ET)
Table '45493355 1' 9-max Seat #2 is the button
Seat 1: holker (1500 in chips)
Seat 2: legendrey (1480 in chips)
Seat 3: Thorup1 (1480 in chips)
Seat 4: ZodiacBrave (1800 in chips)
Seat 5: melon157 (1500 in chips)
Seat 6: harryh4 (1500 in chips)
Seat 7: ScaryPapyrus (1260 in chips)
Seat 8: raul98 (1500 in chips)
Seat 9: thewizard999 (1480 in chips)
Thorup1: posts small blind 10
ZodiacBrave: posts big blind 20
*** HOLE CARDS ***
Dealt to holker [Jd Jc]
melon157: folds
harryh4: folds
ScaryPapyrus: calls 20
raul98: raises 40 to 60
thewizard999: calls 60
holker: raises 180 to 240
legendrey: folds
Thorup1: folds
ZodiacBrave: folds
ScaryPapyrus: folds
raul98: calls 180
thewizard999: calls 180
*** FLOP *** [Ac 5c Jh]
raul98: checks
thewizard999: bets 100
holker: raises 300 to 400
raul98: folds
thewizard999: calls 300
*** TURN *** [Ac 5c Jh] [2c]
thewizard999: checks
holker: bets 860 and is all-in
thewizard999: calls 840 and is all-in
*** RIVER *** [Ac 5c Jh 2c] [7d]
*** SHOW DOWN ***
thewizard999: shows [Kc Qc] (a flush, Ace high)
holker: shows [Jd Jc] (three of a kind, Jacks)
thewizard999 collected 3250 from pot
*** SUMMARY ***
Total pot 3250 Rake 0
Board [Ac 5c Jh 2c 7d]
Seat 1: holker showed [Jd Jc] and lost with three of a kind, Jacks
Seat 2: legendrey (button) folded before Flop (didn't bet)
Seat 3: Thorup1 (small blind) folded before Flop
Seat 4: ZodiacBrave (big blind) folded before Flop
Seat 5: melon157 folded before Flop (didn't bet)
Seat 6: harryh4 folded before Flop (didn't bet)
Seat 7: ScaryPapyrus folded before Flop
Seat 8: raul98 folded on the FlopSeat 9: thewizard999 showed [Kc Qc] and won (3250) with a flush, Ace high

Level one he wants to call a 12 x BB reraise with KQs ?
......and I know I should have raised more on the flop, but in all honesty he's calling no matter what, and I know the check on the turn means he has hit, but I push anyway, just to make sure.