for a paragraph or two, a phone is fine.
When I compose a paragraph such as this one, I don't necessarily enter the words in the order that I intend them to be read. I go back and forth, using Ctrl+left and Ctrl+right to move backward and forward in what I'm writing. I have found moving the insertion point with Android's touch screen input to be an exercise in frustration. I also find it frustrating with Android's touch screen input to select text to copy for an inline quotation and place the insertion point to paste them. Having the parts of an HTML or BBCode closing tag such as </em> or [/quote] spread across three different pages of the on-screen keyboard is also painful, as well as turning href into great or beef when I'm trying to enter an <a> element because autocorrect can't tell markup from prose.
Work emails sometimes involve longer responses and when I have to use a laptop I do.
You are correct that I had work email in mind, be it my day job or free software projects' mailing lists, not noreply@ things like purchase receipts.
Asian languages like Chinese, Japanese and Korean are far easier to input for some people using a finger as opposed to a keyboard system.
I can see your point for logographic languages like Chinese and Japanese. But Korean hangul is an alphabet, theoretically just as amenable to keyboard entry as the Latin letters in which English is written.