I cannot tell you how much that pisses me off. I respond when I'm damn well good and ready, and this has offended some people. When they've said as much, I've been very blunt about how they don't own me or my time, that people have a lot going on in their lives, and the lack of an instant response doesn't mean they are disliked or ignored. However, the likelihood of being disliked or ignored will increase exponentially if such assertions are made. It is funny how when I say that, it generally snaps people out of their punch-drunk, slave-to-technology stupor, and they realise they are being unreasonable. At least, most do. Those that don't are unlikely to receive a response from me ever again.
I often prefer to take the time to compose a proper response, even over email/messenger/whatever. Especially if asked a deep or difficult question. But alas, if such delays are viewed as rude, I fear for the future of humanity.