If you absolutely must know, then the best way to find out is to bring it up with him. Trying to understand someone's motivations based off of very little information can easily go wrong, because it's more complicated than saying that people do so-and-so for such-and-such a reason... all the time, every time, no matter what. The best you'll get is guesswork, and if it turns out to be wrong you might wind up with an even bigger problem on your hands.
I will say, though...
I hate messenging because it's time consuming and leaves room for miscommunication. It doesn't account for tone. I rarely switch it on.
I'm the same. If I'm messaging it's hard to do anything else such as watching a movie, eating, or reading unless I leave a lot of those silences that people seem to hate. I'll do it sometimes to keep in touch, but it's just not my thing. Alone time -
real alone time - is important.
I don't think people leave gaps in communication because they're just not interested in their friends unless they have nothing better to do, rather it's because there's not always something to talk about or they only think of something when their friends aren't online. I have no idea what I'd say to even my closest friends after a few days if we spent the majority of the time we're both home or at the computer IMing.
