IDK man .. many services really just don't even want to deal with a sign up they are never going to reach. By using a disposable email, you're telling the business, I want to use your service, get value, but I don't really want you to reach me. To them, it sounds like a loss loss situation. Business are there to make money, and they offer a signup/trial/free account so they can give you access in exchange for being able to reach you.
But I do sympathize with the stupidity of marketing email madness.
But I do sympathize with the stupidity of marketing email madness.