Dashes in League

Ok, so during one of my many sessions playing League, I decided to play Galio and bunch and I found it really upsetting that he couldn't dash through walls. After thinking about that for some time, I realized that he was the ONLY champion that can't dash through walls. At first I thought it was because "Oh, he's a giant, he's too big to go through walls". But that wouldn't make sense since he's a a colossus that can punch through mountains. I'm not necessarily asking that he should be allowed to dash through walls, but I would like an explanation for why he can't. (Also if I happen to miss any champions that also can't dash through walls, I apologize)