Even when I try to use my phone, I often have issues with the website I'm ordering from. Try on my laptop and it usually works fine. The truth I think is that developers build on desktops/laptops, so they test more there. It's easier for them. This makes it more likely for bugs to crop up anywhere that gets less testing. I myself have not always tested all of the "safe" changes I've made (on every browser/platform).

And yes, as a generation who grew up with the extremely user friendly form factor that allows tiled windows, easy tab switching, and shortcut keys... Giving all that up to not have to get up off the couch seems silly most of the time.