Because as Terry Pratchett astutely notes in the Hogfather belief is what makes the human society possible. We invented justice, mercy, duty, laws, money etc. They exist only because we believe in them. Some beliefs make the world better, other ones worse, and we should try to emphasize the former and minimize the latter.

Read the book Sapiens.

Being able to believe in fiction is what allows humanity to function.

Belief isn't inherently bad you can believe in observational facts. It's faith that's dangerous. Any system that requires you to maintain beliefs without observable facts or in the face of negative confirmational facts is a problem.

I always liked the line in Dogma about them, don't turn ideas into beliefs, you can change ideas easier than beliefs. Paraphrased and I understand how much it waters down the whole problem but I still thought the idea of it was nice. Listen and be open, you shouldn't always need to be rigid. Though mean there are still ideals I'm rigid about, respect, compassion and such. Though I always thought the idea was you thought about what worked best for everyone not just what people said you should do cause tradition.

I believe I'd like another drink.

Well yeah. What you believe is literally all reality is. Of course it's important. I believe I'm sitting in a chair typing on my phone right now - if I didn't have those beliefs, my reality would be completely different. That's important

They do indeed.

My parents are deeply religious, but have never figured out that it's my siblings and I who actually answer their prayers.

I think a lot of the time "beliefs" are more about social signaling than actual worldview. Most people aren't going to do anything to go against the grain for the sake of their beliefs, so one belief or another isn't going to make a difference for anything that matters.

The difference between a belief and a theory is no one was ever burned at the stake disagreeing about a theory.

In my view, beliefs are important. To me, a person is built from their beliefs.

Beliefs are mutable and can change for all sorts of reasons, at all sorts of speeds, and in all sorts of ways. They're not permanent, but I do think they're fundamental to the character of a person.

People do that. Like kids talking about their favorite baseball team. The same focus on things that move them to the core, while having no effect on to their life apart the place they willingly give them.

if a belief is a model/theory/assumption that a person will not change regardless of evidence against it, it is by definition a delusion.

If a belief is an opinion, it is a personal statement. Statements like “Vim is the best IDE” are really conveying the information “I prefer Vim over all others IDEs” which is a true statement.

If a belief is a hypothesis then the person holding it will accept if it ends up being wrong.

Only in the first and second cases do people usually place importance on their beliefs, and typically, only the first case leads people to harm others or themselves with no way to convince them to stop.