Mobile operating systems are designed to engage and distract the owner. Lost your attention for a few minutes? Screen dims and threatens to darken! Oh no! Touch its face and keep it alive! Notifications from everything. Alarms that won't shut off until you do something about it. Pleading with us to recharge the battery. Insisting that radios be turned back on and sensor access be granted.
Every app, every website you visit is infested with dialogs and pop-ups that you're brushing out of the way, trying to get something accomplished.
It really tests your resolve and concentration, to see if you finished that one task you had in mind when you unlocked your phone, without going into 5 more on the side, or whether you can tame your phone sufficiently to be an assistant or productivity tool, rather than a firehose of marketing from dozens of companies to you, the consumer.