Since the question says "everyone" away.. I'd lean towards Avoidant attachment issues. AKA fear of getting too close or hurt. Some people can't accept love or feel they lose control or their independence. I'm sure it's nuanced.

Low self esteem, not believing others when they are nice to you thinking of it only as pity. Being self absorbed and overly ambitious, instead of seeing life in a less selfish way that everyone struggles.

The cure is to realise you don't need to control everything, you aren't the main character, and to change your intentions.. sure you might be messed up, sure some people will push you further into darkness but accept you aren't without flaws and that you'll mess up a lot then you're well on your way to living in less pain.

Fear, unwillingness to heal, and trust again. Mostly their reasons are all internal and could be remedied if they took the steps to kove forward in healthy ways. Most don't because it's too hard.

Joke and assume all you want people, but there's a reason and it doesn't involve blaming the person who is afraid.

If life hasn't been kind to one, general distrust due to fear of being hurt again can be a major reason.

Been abused and hurt too often in the past

Herpes?

I couldn't tell you 🤷🏻

Such low self esteem that they think it's only a matter of time before they are figured out and rejected. Then they bring about a self fulfilling prophecy by pushing everyone away and behaving so badly they do eventually get dumped .

Insecurity and anxiety

Wisdom?

Understanding what they thought was love was actually being used.

Fear of commitment or rejection.

Fear of being hurt

Trust issues.

Looking at the bill.

Fear. Being smart i guess. 💔 is no joke

A need to find inner peace before dealing with anyone else

Pineapple on pizza

Getting burned one to many times

Having been rejected so many times in the past that you internalize it.

They think other people have cooties?

Sooner or later their mask falls off

When a guy you just met starts talking about his desire to have kids before he even kisses you for the first time.

Calling everyone a nazi/fascist