Why no doorbell cams?

Hi all, I’ve seen a lot of posts from owners who have drop ins, walks, and house sittings where they’re questioning if the sitter showed up, how long they stayed, etc… If you’re having someone enter your home when you’re not there, why don’t you have a doorbell camera/camera at the door? You can get rechargeable ones for around $130 and see all entries and exits from your home. I’m genuinely curious because I just couldn’t imagine having someone coming into my house when I’m not there and have no oversight whatsoever, but maybe I’m just crazy.