Bleach has actually had a more respectable reputation with fillers than most of its bretheren, though this is not something you would notice during the US broadcast.

Where its pals like Naruto and DBZ would do extended fillers to give the manga time to catch up, I know Bleach has at least taken a break entirely from broadcasting instead of doing fillers. So, if Bleach were more popular, there could have been *more* fillers.

Thing is though, these shows are made for children, and they are made to sell toys and keep a franchise going. The more popular shows can't afford to take a break, to give children a chance to latch on to another product. It's all business related. Children really do have lower quality standards so companies can get away with the filler as long as they fulfill certain requirements in an episode. They dont' care about 'us', the older people, because we are not buying their toys.

So for the most part, I no longer watch shows that are made for children and value having their product in view at all times more than maintaining a consistent quality.

As for DBZ, dude, these new shows have far surpassed DBZ's level of pointless fillers. However, I've mentioned here before, there is a 'new version' of DBZ showing in Japan now called Dragon Ball Kai. It is astounding just how fast it is going by chopping out all of the fluff and keeping the pacing closer to the manga. The last episode of Dragon Ball Kai I watched was episode 7, and they were doing stuff there that originally happened in the 20th episode. Twenty! They have the luxury of doing this not only because the manga ended a long time ago, but the animation was finished a long time ago too :P

There are a lot of anime that are created from 'finished' manga, but they tend not to be of the Bleach/DBZ level Shounen variety, and not nearly as long. Filler is less of an issue if the anime company is not trying to establish a franchise off of a currently running manga.