I honestly don't think it is willpower, it is simply that I never had to break the "addiction" because I never had it in the first place.

I always found the form factor extremely limiting compared to a desktop (it's the same reason my laptop ended up running a TV upstairs, the idea of programming on the sofa sounded great but in practice I'd get frustrated and immediately retreat to my quiet downstairs office with multiple screens when I had to do something tricky/requiring concentration).

Where I do use something that optimises for distractions, I look for how to minimize the distractions (e.g YouTube - I use the excellent Unhook (with Ublock Origin) which turns the YT home page into a search box and little else, hides mixes, shorts and other distractions) and make it work for me.