People know the alphabet as a one-dimensional object. Unless your keyboard has 26 keys all in order, the multiple rows don't correspond to an existing mental model. At that point, you can either choose qwerty, which pleases anyone who already knows it, or you can make a sort-of alphabetical layout, which pleases nobody.

I'd be curious about your statement the most people who use phones didn't learn to type. Is that for a particular age group? Alternatively, for the developing world, where phones are more common than computers? I'm having difficulty seeing the justification for the statement.

If you know the alphabet you can easily guess where the keys will be. (In a alphabetically ordered keyboard)

Do you believe that most people who use phones know how to type?

If the keys are laid out in a 1x26 keyboard, yes. If the keys are laid out in a more usable way, then no. If I can see the key 'j', I cannot guess whether 'm' will be to the right or left of it, without knowing the length of the row, and considering it at all times.

I would describe today's society as one in which typing is necessary for any basic tasks, and is universal, and so I don't see why smartphone users would be different from the norm in terms of typing ability. Are you using "typing" to refer only to "touch typing"?

That is a good point, although one could easily point out that “alphabetical order” is also a completely arbitrary convention, and we could just as easily argue whether we ought to change how we teach that order. Perhaps a different ordering of the alphabet, like sorting by usage frequency or grouping the vowels and consonants together, would help everyone learn to read and write. The same type of argument could apply to nearly anything. For example, in the English language, perhaps we should standardize spelling. This isn’t a novel suggestion. Mark Twain famously and perhaps apocryphally made such a suggestion. Why not just teach everyone in the world Esperanto or Lojban?

But my argument didn't involve teaching anything to anyone. It was simply accepting the fact that most people are more familiar to alphabetical order.

What benefit is there to having everyone hunt and peck on a phone to keep with a convention that only really makes sense to typists?

The hunt-and-peckers will still be hunting and pecking on an ABC keyboard, at least the typists don't have to. Also, the first adopters of smartphones probably did have overwhelming keyboard experience, so I can totally see how we got here. Fortunately in phone land the default is just that and easily changed by anyone who thinks another layout would work better.