No keyboard, no mouse, tiny screen. Every single action you'd like to take is slower and more cumbersome. Want to selection a portion of a URL? Well, get ready for an adventure. Tap the URL bar once, then -- oops, now it thinks you want to copy. You can't tap the individual sections. Try to move the little "copy bars" but oops, the press didn't register because they're tiny. Spend about a minute randomly pressing the URL bar until you can actually get the behavior your want. Or, try to switch tabs. It's not hard per se, but it's an order off magnitude slower than ctrl+tab. Or search within a page. Can you just hit ctrl+g and start typing and then press ctrl+g again? No, no, you need to enter a menu, enter a submenu, then wait for the onscreen keyboard to show up, then glide your finger over that with a few corrections, then move your finger down the the tiny next button.

It's all objectively terrible, and it accomplishes nothing except allowing the user to use the internet right then and there.

Phone networks by design track you more precisely than possible over a conventional internet connection to facilitate the automatic connection to the nearest available network. Also, for similar reasons it requires the phone network to know that it is your phone