> Wi-Fi Ad-hoc. It never gained widespread use.
I don't think this is true. In the early 2000s, in Germany, the alternative, now vastly used "infrastructure mode" was rare because Wi-Fi basestations were rare and expensive, e.g. DSL modems didn't have built-in Wi-Fi.
So the only way of wirelessly sharing internet at home / files with friends at university (which also didn't have Wi-Fi yet) was with ad-hoc mode.