It's absurd to not allow clearly-marked-but-wholly-readable proxies at Cube events, but I guess I see such low-effort proxies at EDH tables around me that there's some logic to drawing the line at the easiest point. To be honest, trying to read low-res Magic cards is headache inducing during a game, but even so!
"No proxies" feels really weird to me because you're going to have complete strangers drafting your cube, which is a process that involves directly (man)handling the cards. That just seems like a recipe for disaster.