Technically BSNES is not accurate, at least according to it's author. It's just it's much more accurate than ZSNES and SNES9x, and accuracy of emulation just happens to be much less critical in SNES games than in NES games. In summary, the most powerful/complex a system is, the lesser the software will require on dirty hardware tricks to do their stuff, and the lesser emulation accuracy will be required.
ZSNES is and has always been the Nesticle of SNES emulators. Except it has no tile viewer...
Enough to have every game working fine (which is not the case of Zsnes/Snes9x), and that what is called accuracy in my point.
Just try to play Der Langrisser on Zsnes (except if they finally fixed it) for example then you will probably think accuracy is as much important on SNES than on NES.
From now, at least, everything that I tried on Bsnes also work on the real hardware (a SNES) which isn't the case for Zsnes/Snes9X (which sometimes create bugs that aren't produced on a real SNES).
About the need of accuracy on SNES : http://byuu.org/bsnes/accuracy
(and there are probably a lot of games not listed, like Megaman X2 for example).
BSNES runs like someone with their tendons sliced on my computer, and since I've already gone and fixed my problem, I'm perfectly happy wallowing in the crapulence of my inaccurate emulators (because I don't care about accuracy as long as the game runs).
Short answer: apathy.
Are you sure you tried the good build ? (I mean, "accuracy build" really need a powerful computer, but that's not the case of the compatibility build). Or else, you really have a really old computer ?
About the accuracy thing, you'll probably change your mind when you'll play a game for 20-30 hours and finally notice the game is broken.
FallenAngel : You can still take an old build. I'm with you about that, I don't really care about cart-folder or multi-emulator system so I just stick with the last stand-alone version.
Anyway, I'm not here to judge people, they can use what they want, I just find that rather weird. It's like having a Core2Duo (or better) available at home but still want to use a Pentium II just because it's still working fine for many tasks.
About romhacks which only works on ZSNES or such thing, that why I wouldn't never trust an emulator (not for the final beta-test, at least) and still test the romhack on a real SNES to be sure.