Assuming it’s a womxn asking the question and she is looking for a man’s perspective, I (who identify mainly as masculine) feel at liberty to shed my humble view on it. Assuming he isn’t just a couple of old hot dogs inside of a very tiny, mohair sweater which would make operating an electronic device very difficult, there are a number of reasons I can think of, which I’d like to list from most probable to least:

1. He’s a dick. I list this first because a lot of guys are actually assholes, they don’t really care about anything but themselves. To be fair, it probably isn’t deliberate, more a general inconsiderateness towards anything but me, myself and I. Is that why you are attracted to him? The classical bad boy attraction, maybe there’s something to it?
2. He’s buzzy. A completely lame excuse, basically the same as point one. What could be so important that he can’t spare a second to message you saying he’s buzzy? Which brings us to point three.
3. He’s not thinking about you. He’s on your mind much more than you are on his. It’s not what you want to hear, but maybe you have to face the reality of it: he’s not that interesting after all, he’s a dick.
4. He’s playing games. He wants you to want him, being in control is prime objective. Which basically makes him an even bigger dick than mister One.
5. He only messages you when he’s high. Haven’t you only texted someone when sober you would have preemptively hidden your phone? And that is exactly why he/she is the one you’ll text as soon as you’ve drowned all rational thought. Maybe he’s taking some time off from partying?
6. He’s shy. He’s the total opposite of Dick from point one, he’s one of the good guys. He doesn’t know or is unsure how to approach you. You don’t want someone to pin you against the wall, and you appreciate the gentle touch? Then take on the role traditionally expected from men: initiative. If you are willing to take the lead, this could be your dream scenario.

Disclaimer: I am aware that this post is quite sexist in some ways. I’m not sure it is more disrespectful towards womxn or men, possibly both, as most sexism is. Please feel free to leave a comment bellow, I’d love to discuss this.