The assumption when writing this article is that the guy that you're texting is not a complete asshole, and isn't replying for any number of asshole-related reasons (e.g he's with his girlfriend and doesn't want to get caught, he's too lazy and just isn't bothered). This list of reasons applies to genuinely nice guy who for one reason or another just doesn't want to text you back. And in these cases, it's much better for you to move on, rather than becoming desperate and sending text after text with no reply, like some sort of creepy stalker.
You're Coming On Too Strong
Most guys are pretty easy-going when it comes to dating, or at least want it to make it seem that way. And they are attracted to girls who have a similar attitude, or even a slightly dis-interested one. Guys are always more attracted to girls when they feel like they have to chase her a little. Now I'm not saying playing hard-to-get is always the right way to go, but doing the total opposite and appearing way too keen is never the right thing to do. It will scare him off, and he'll most likely get the impression that you're desperate.
He Doesn't Want To Give A False Impression
Although it's a little childish, some guys won't be texting back because they don't want to give you the wrong impression that they want things to go any further. They might write back now and again to be polite, but if they aren't replying as frequently as they should be then it might be time to move on. If you think this is what's happening, it's probably best to just ask the guy outright, rather than keep texting and building up false hope for yourself. Just don't be weird about it.
Too Many Questions
Much like coming on too strong, asking too many questions can also scare a guy off. Guys are pretty simple creatures and can usually only deal with one thing at a time. So if loads of questions are coming in at once, especially if you've only recently met, chances are he'll eventually just give up trying to answer them all and end up just not answering any. Better to ease yourself into it, and to find out more about him in person, rather than playing 20 questions with him through texts.
You're Boring Him
Being good-looking can only get you so far, and most guys, again talking about the decent ones, will want a little bit more out of a person than just the fact that they dress well and have nice hair. You don't have to have the exact same interests as him, just that you have some interests, and are interesting to talk to. Chances are that if he likes you, he'll start to take an interest in these things too.
He's Trying To Play It Cool
From the girl's point of view, this looks pretty similar to when he doesn't want to give you a false impression, so again the best way to get rid of any confusion is to just ask him. The only reason he's doing this is to not come on too strong to you, which means that he likes you. So if you do ask him what the situation is, he'll be honest and say that he is interested in you.
It's Too Late At Night
Guys love sex, but they don't like enough it to fell like they're being used. And if you're texting him at 3am, chances are its for a booty call, and chances are he's not going to be up for it. And sorry for sounding like a girl when I talked about being used, but I couldn't think of any other way to say it.
You're Being Too Needy
If you've only recently met the guy, but you've already started getting emotional in your texts with him, he's not going to respect you, and he's going to be turned off very quickly. Guys like to be needed and to look after girls, but not if they've only known them for a couple of weeks.
A Genuine Reason
Sometimes there actually is a genuine reason, like he doesn't have any texts or data left to reply to you, or he's at a football match or he's with his friends. But the key thing to remember about this situation, even though you don't know if it is a genuine reason, is to still be patient. He will reply to you eventually when he does get a chance, and will apologise for the delay (if's a decent guy), so any extra texts you send can only harm your situation.
He Doesn't Like You
This is the biggest fear when he's not texting you back, especially if you really like him. But unfortunately this is the case sometimes, and it's just important to remember to not get desperate, because you're never going to change his mind like that, and to just try and move on.