Said entertainment can come in a few different forms. You can either have fun with your phone's stock capabilities, playing with its camera and its cooky modes and filters (*ahem* Sony), reading news and gossip from a built-in news bulletin, or browsing the web. But there's also the obvious choice of downloading apps and games from your respective app store.
And there are a lot of entertaining apps out there. Sure, they are not labeled as "games", but camera apps like Snapchat or MSQRD, karaoke apps like Triller, or educational apps like Space Walk 2 can definitely put a smile on your face while you navigate an otherwise mundane weekday. That, or you can just go for a quick fix from one of the many mobile games available — from frantic tappers, to adventure games, platformers, or even shooters.
Some people don't enjoy mobile games as a general rule — either they are far too simple, or far too engaging to play on a phone and on the go (XCOM?). Others could care less that Vine is gone and would rather play another level of Candy Crush. Which side are you on?