It's not as if Snapchat are a tiny company with nobody smart enough to notice there's a camera API, this is intentional.
If you want to send a quality photo to a friend, there are apps for that.
you literally take photos and send it to people
This hasn't been the primary focus for years. You can now send Snaps that don't expire after a time limit, and can save your snaps to your storage or Snap's cloud storage (called "memories").
If I was making an app with photo taking capabilities, I would explore the Snapchat route. Obviously Snapchats users are ok with this for the most part.
I have made countless cross-platform AR apps for mobile and desktop. Never an issue with WebRTC/getUserMedia, iOS, windows, etc. However Android is always a nasty problem. From incorrect aspect resolutions, image stretching, silent fails. Each device needs a custom fix which is time consuming and costly. No wonder why Snapchat went an alternative route.