does anybody know why this behaviour was chozen?

More important, I think, is the question "why doesn't use warnings; warn about this?
I think this is the real question here. I too have been bitten by this behaviour and while it didn't cost me hours to debug, it did slow me down and was annoying to find. I don't know why use warnings; doesn't warn about this. I wish it did :-(
After all, we already get messages such as "Useless use of a constant in void context at...". Why not something like "Useless use of an empty list in loop context at...", or something similiar.