There's a phenomenon about dances that I find utterly fascinating. If you want to dance with someone you don't know well, it's good form to ask permission from their date first. The date normally says yes, so why even bother? Wouldn't it be kind of rude to say no? Maybe, but it'd also be rude not to ask.
Some questions seem unnecessary merely because we think we already know their answers. 'May I ask your date to dance?' 'Would you help me with this bag?' 'May I put my equipment in this closet?' (That last one's just for me.) You'll probably get approval, but the main point of those questions isn't to get a response. It's to communicate your empathy to the person you're asking.
Asking permission shows you understand that the other person would be doing you a favor. It demonstrates that you're not taking the favor for granted and that you value their feelings and concerns. The response will probably be yes and you may not need to ask again, but it can be terribly important to ask the first time.
So if you don't think you need to ask for a small favor, consider what the mere act of posing the question would achieve. Will it show that you care about the slight inconvenience granting the favor would cause? If so, do it anyway. It'd be rude not to ask.