Multiple camera angles are used for two reasons:

1. Added visual interest. People tend to want variety and colour and movement offered by different views can provide that. This is the obvious reason it's being used.
2. Ability to edit without it being obvious. Often a presenter will require multiple takes to "get it right". If you edit in the take, the picture "jumps" because humans move around. If you have multiple cameras you can edit and switch cameras without it looking like an edit. If you then also look at a different camera when you make a mistake, you can keep recording and fix it when you edit it together.

Style over substance IMO. Trying to keep people's attention visually in case what they are saying isn't interesting enough.

If they had a second angle camera locked off on them from one side, and occasionally cut to that shot without turning to face the camera itself that'd be alright, and it's a useful tool for disguising edits, but needs to be done in moderation.

Just another reason not to watch them. I don't want to watch any videos of talking heads. There's no reason that I need to watch a video of someone's face talking about anything.

If done well, it can add to the feel of the production quality. Otherwise, it’s just another camera. Maybe a bit jarring, but I don’t particularly care

Imo it might create somehow the effect of "now, pay attention".

Takes away from Mise En Scene

It's just the new trend. One person starts it and has a successful video, and then everyone else follows it regardless of whether or not that was the reason for success. But I'll take it over constantly using jump cuts every 5 seconds. That shit has been obnoxious for years. Most of the things I watch on YouTube these days are educational stuff so I don't see either of these things that often. The only time I'm okay with the multiple angles is if they use it as like a "tangent camera" for when you know they are going off script or just expressing their opinions on what they are talking about. You know, an actual reason for two cameras instead of just "oooo look at me."

The YouTube trend that's been pissing me off are the YouTubers that change the thumbnail and title an hour after it's posted because it's not getting enough views and then make a community post talking about how it's the best video they ever made.

It’s a PITA.

If the cameras are all right next to each other it’s fine. Otherwise, their eyes get all wonky and I really don’t like it, it kind of makes me uncomfortable