I have a terminal app in my phone, but I don't normally use it from the touch keyboard..

The main reason I have it is because from it I can install an ssh server (and a few other services, like privoxy and so) and then connect to the phone through ssh and access that CLI from other locations, even places where the internet is restricted/monitored or there isn't a wifi access point (I can create a hotspot from the phone instead). If you are using a work laptop with restricted access, or are traveling and using a computer in your remote location, carrying around with you, in your pocket, a set of CLI / TUI tools and apps that you are familiar with can come in handy.

Also, nowadays you can plug a keyboard directly to your phone (a monitor too) and have it work as a portable terminal device. Of course it would be better if you were able to have a Desktop-grade OS in your phone for this.. but things like termux work if you are a "terminal junkie".