It does when the end user is being a NAT and a firewall and they don't know how to configure it. Legacy IPs cameras are notorious for being difficult-to-impossible for consumers to install, and when they managed to do so, they were often set up insecurely.
The typical MJPEG/ONVIF camera doesn't even remotely compete for the same customers as Ring/Nest/Blink.
Security cameras are the classic example of widespread self hosted but internet-accessible.
Even the ones that have proprietary apps are often just alternative frontends to a web server running on the home network.