If you categorize all desktop apps ever made as "legacy", sure, it's hard to see why people wouldn't use a Chromebook.
On the other hand, non-technical users are happily torrenting shows and movies, playing 3D-intensive games on Steam, making somewhat decent-looking documents with Word, making gifs with a pirate copy of Photoshop, etc.
A Chromebook offers (generally inferior) alternatives for some of these tasks, but not even all of them.