Well, welcome to online dating, OP (or just dating in general) - and not just for gay men, but for men and women, gay and straight. There's a lot of flaky behavior. But some thoughts (based on my experiences and observations):
- sometimes they're just not that into you, or they're only "kind of" into you but don't think it merits a "no" or a clear rejection. So some resort to continuing to exchange polite messages, but hope their slow or non-responses give you the hint that they're not that interested, or hope that your interest in him will die off naturally due to his flakiness.
- I think people make the mistake of assuming they're the only person having a conversation. Some men / women are juggling multiple messages and potential dates online at any given point. They may say they're interested in continuing things with you and mean it, but then soon find someone they think has more potential. Again, they don't want to give a clear rejection and cut off their options, but they're not going to push to make another meeting happen while they explore other dates - they buy themselves more time by drawing out the next meeting.
- Sometimes they're really just busy with other things in their life - a job, family, stress, travel, whatever. Even though you might be focused on when you'll hear from him next, texting you or logging into a dating app and keeping up with messages with a person he's only met once or a few times might be low on his list of priorities. Heck, some people are really bad about getting back to you for personal and business e-mails; don't expect prompt follow-up from everyone for dating messages either.
- Finally, sometimes they're just flaky assholes who are unable to practice common courtesy.
In short, I've found that if a guy's really interested he'll try to keep up communications, except in cases of delay because 1) he doesn't want to appear too eager and overly invested, or 2) sometimes he wants to hear from you first to evaluate how interested you are in him. If you've initiated communication and you're not hearing from him, just give it up as a lost cause and move on, and in the slim chance it really was an honest mistake on his part, he'll follow up with an apology to get back in your good graces.