It's more that phones are built to be tracking devices, so 99% of normies use them as such. The most prominent example of this is how by default, both iOS and "normal" Android require a persistent account to use which is also used on many other platforms (Apple ID, and Google account, respectively), and they come with telemetry services which allow the parent company (again, Apple or Google) to essentially track everything you do at will, and store it, associating it with anything else you do on your account. E.g. are you signed in to Google Chrome on your PC, and do you use the same Google account on Android? Congrats, now your geolocation data (phones have GPS, remember?) can be correlated with your browsing history. And once Google knows your commute and habits, you don't even need to have your phone in your pocket for that.
And when it comes to internet browsing specifically, phones also do make a difference. Something like 10% of people on desktop use an ad blocker (of which the good ones also block all kinds of tracking scripts). On mobile? Used to be that Firefox was the only mobile browser that supports addons, and hence adblockers. Firefox market share on mobile? Something like 0.5%. Even if every single Firefox user on mobile installed an adblocker (fat chance), there'd still be 20 times fewer ad blocking users on mobile than on desktop. But notice that I said "used to be". Today, Firefox no longer supports addons, unless you use the Fennec build from F-Droid. I'm gonna guess the F-Droid marketshare is something like 0.01% at best. Maybe even an order of magnitude or two lower.
So it's possible to install AOSP with no google services (optionally with microG with capability), use exclusively F-Droid for apps, use an adblocker, root your OS and use AfWall+ to gate apps. Or today you can even buy a Pinephone and have an outright Linux phone with zero google or apple code (and some caveats like not being normie-ready yet). But among the general userbase, 99.99% of phoneposters - especially ones that are retarded enough to be easily identifiable as phoneposters - are going to be thoroughly compromised.