It's not so much the business context as the email context that puzzled me. Starting an in-person conversation with one of those "can I" questions costs at most twenty seconds, so if it helps you feel less nervous it's easy to see it as twenty seconds well spent. But do the same thing at the start of an email conversation and it might be days before I remember to reply to you!

(Not you, that is. I'd hope that if you emailed me I'd reply more promptly than that. But if you were someone I'd never heard of, it would depend entirely on how busy I was.)