I agree that it is annoying to have the "home" or "main" link go to the blog home. But when you are at blog.domain.com, is it really that difficult for you to figure out how to get to domain.com?
Yes, on mobile phone it might take a few tries just to alter that web address, especially when the domain name looks like sslmadomaiinnahas. Try remembering that. Navigating to the front part of the url to copy that domain is borderline impossible on tiny safari screen. Clearing the blog part or the part after domain/long-url-ending can also make you rip your hair out because your device might delete the entire url.