I think じゃあ、早稲田まで isn't polite but plain. じゃあ、早稲田まで行ってください and じゃあ、早稲田までお願いします arewould be polite.
Sentences without です,ます ます aren't polite, so the sentences that end with particles like 早稲田まで, ほしいから、and, and 別れたから aren't polite. And どうして? isn't also polite either because ofit's without です,ます ます.
I think omission of です,ます ます always makemakes sentences casual / plain.