Why do people do this?

I have this recurring issue of people who add and/or message me like they wanna be friends, but then they seem to suddenly change their mind and unfriend or block me. This occurs on things like Snapchat, Roblox, Discord, etc. And I just can't get through my head, why people do this. If you don't wanna be friends, then don't add me to begin with???

You could say that they changed their mind due to not liking my personality, however, while that may be the case sometimes, there are cases where they do it within a few messages. For example, this girl I added from an app for making friends called Wizz. We talked on the app, so then I added her on Snap. We said hi to each other, and I asked if she played Roblox. She said no, then I asked if she played any games. Then she just… unfriends me? You're changing you're mind that quick when all I did was ask if you play games…? That's a perfectly normal question, it's not like it's something inappropriate or personal.

Another example is a time I added someone on Snap from an app, I forgot which one. Due to the many previous occurrences of people unfriending me suddenly, I asked her for clarification on if it's alright for me to text her, because I didn't wanna bother her or anything. She specifically said, yeah it's fine you can talk to me. And so I was like alright. And guess what? Shortly after this, she unfriends me. WHY DID YOU SAY IT WAS OKAY FOR US TO TALK THEN?!?!?!

I have many more examples, but this thread would be massive if I listed them all. But they all follow the same basic idea, someone adds me as if we're gonna be friends, either because we met in a game or on an app, we talk a bit, and they abruptly change their mind and unfriend or block me, despite me saying nothing wrong.

People just seem to suddenly change their mind without any clear reason or hints that they might do so, such as noticeably being less interested in the conversation, regardless of what I say to them. I do not say anything inappropriate to them, I talk about literally normal things. Why do people do this, when they can just… not add me in the first place if they don't wanna be friends…?