There are a few reasons.

1. There's the religious aspect. To most Buddhists, Buddhism is a religion and the texts are sacred.  They are so sacred, that simply chanting them is believed to bring merit. So you've got people chanting Pali (which they don't understand) in the belief that merely saying the words will bring supernatural benefit.

2. Even outside of religion people venerate older texts. For instance, people still read the works of Plato today, even though he was wrong about a lot. Schools require reading literature from hundreds of years back, even though there's a lot of excellent literature that's been released since. Others insist on reading original works from authors (like Kant) even though the works are widely acknowledged to be poorly written and even though excellent third party sources exist.

3. The Buddha was believed to be enlightened, and since he got there, he's seen as the best source of information on that subject.  Well certain texts are believed to be closer to his words (e.g.: because they're closer to his time or part of a school that claims it's closer to his vision, etc...) so by their perceived proximity to the source, they are seen as more accurate.