Honestly it's a pretty good way of compartmentalizing projects in your mind.
You usually remember pretty well what language your wrote a project in.
And if you want to find a project again you just have to look in that language's directory.

Second advantage is that if there's a language you only fucked around a little for fun, it doesn't clutter the directories of your most used languages.

for me the project exists because I thought "id like to play with today" but not necessarily "I want to make a project"

I agree, just have it by project. Otherwise I might have to look in different folders to find something. And what does it add, that something is grouped by language?