How come you let voters decide the best answer?

Because you were sold a bill of goods into thinking that this was a Q&A site. It's not. It is merely a way to garner points.

Some folks do not know how to choose a best answer; others are too lazy or careless to choose, which means the questions roll over into letting the general membership choose the answer and that means ANY answer can be the best answer, even if it is not the 'best' answer.

Sometimes the askers are overwhelmed by the number of good answers, they cant decide for themselves, so they leave it to voters.

may be some are just lazy.

some just want lots of answers, and leave it open.

then just for get about it.

so it ends up in open vote.

more and more questions, seem to be ending up there.

Some people just vote for any answer withiut thinking that it is the proper answer or not.

because the asker doesn't bother to choose so to resolve the question someone's gotta do it.

Some forget, some don't know how, some want others do do it and others just don't care.