AOL didn't use to let you leave AOL. For many years it was a 100% isolated walled garden. That is what made AOL AOL many years before AOL became an ISP.
They only grudgingly started adding ways of accessing internet content as the growth of the net so outpaced AOL that they had no alternative in order to keep subscribers.
And, if memory serves, when they first began providing access to the Internet they also charged extra for it (although I may very well be mixing them up with someone else).
I remember for a while on Usenet arguments were won by simply pointing out the other person had an @aol.com address.
Also, in some countries such as Germany, WhatsApp serves as a virtual mobile provider.
https://gigaom.com/2014/04/08/whatsapp-becomes-a-virtual-car...
It's like 1000 free minutes, nothing else.
Becoming a virtual provider works with E-Plus, that's why there are very innovative ones in Germany. I use simquadrat.
It also turns the dynamic of the web, where you actively seek out information through search and by following links, on the head, by pushing information to you, forcing you to at least acknowledge them. It has a similar ad-ridden, homogenous aestetic as AOL, practically unbearable without some ad blocker.
The Facebook app, on Android at least, uses a built-in browser when you click a link.