Benko Gambit eventually always accepted

I am a player of the Benko Gambit and what I've noticed is that they'll often decline the gambit, and that disturbed area of him attacking my undefended pawn remains.  We'll be developing like normal, fianchettoing my king bishop, playing d6, playing Nd7, etc. but in the end they'll ALWAYS accept my gambit.  They also play a mistake.  They also trade of light squared bishops.  It's a mistake because my light squared bishop is not as important as my dark squared bishop and it's the opposite for him.  So I get an even bigger advantage...  Then I start harassing them on the queen side as with any Benko Gambit position. 

So my question is, why is it that they will always accept the gambit even though it may not be right off the bat?

post a game?

In response to the OP, accepting the gambit is the strongest, and the bust to the Benko.

Sure, some players will play 5.b6, just to try to plug up the Queenside, but White's strongest move is to take the pawn, and then there are two lines where White gets a big advantage, one of which even Kasparov (not Garry, the other one) acknowledges in his book from a year ago as being a problem for Black in his addendum at the end, and those two lines are the Fianchetto Variation (which even Kasparov agrees) and the King Walk variation, where the LSB's are traded, but not at White's accord, at Black's, where Black takes on f1.  White taking on a6 only accelerates the play for Black.

I still to this day will never play the Benko Gambit again as Black, and will never advocate the Benko Gambit to anybody unless they want to lose.

The same can be said, by the way, about the Alekhine (Black) and King's Gambit (White).  Don't play them!  You'll simply get creamed every time once you start playing against players that really know what they are doing!  I've played my fair share of games against players 2200 to 2650, and am well aware of what can and can't be played against these guys if you want any chance at all!