Yelp is extremely hostile to web users on mobile and shoves their app at you, actively blocking mobile functionality. You have to spoof user agent or request desktop site to use their service. So after realizing how hostile they are, I stopped using their service. Wasn't aware of their shady business practices in the past, and I think they've improved somewhat? My main issue with them today is their subverting of mobile web usage.
Similarly, Square Cash hides their login page on the mobile cash.me site. You have to request the desktop site and actually go to cash.me/login to have any chance of using their mobile site. It's fucking crazy.
Twitter and reddit drive me up the fucking wall. Twitter removed most functionality if you aren't logged in and hits you with a popup about once every 0.1 seconds as you scroll but gives up when you close it about 6 times. The mobile reddit site is just straight broken. Images disappear if you click in the wrong place, video doesn't work, can't change search options, posts act like they fail resulting in duplicate comments. Yet they have the audacity to push their shitty app down your throat every other page which is just a webview of the mobile site with the same problems.
These companies will do anything to inflate their user count and get more access to more data to sell. Instagram is particularly egregious about inflating user count. You can make an account without even verifying your email, but you can't log in again or even delete your account without linking a valid phone number. There is probably a 7 figure number of abandoned accounts like that.
Add Pinterest to that list of super annoying services who won't let you even look at anything without signing up/linking up/whatever else they could extort from you before letting you look at a simple picture.
Similarly, Square Cash hides their login page on the mobile cash.me site. You have to request the desktop site and actually go to cash.me/login to have any chance of using their mobile site. It's fucking crazy.