Why is something so simple like interacting with other people so hard to do?

Because people mostly suck, and have selfish intentions.

Because people are scary.

I have no idea but I know te struggle all too well. I suffer from severe social anxiety disorder so social situations are never easy and I often am not even sure how almost like I lack some of the skills I need

Interacting is not difficult if you don't interact with difficult people I find.

I've never found it hard to do. The trick is to not give a damn.

Are you an introvert?

idk dude you seem to be interacting with me quite well. Just do the same thing to others (not exactly the same though, that's just creepy and weird)

I have no problem