Let me kindly point this out to you, and explin a little bit about the "rules". Childish or not, we follow them because appearing desperate is the WORST thing to do aside from being a creeper. Usually those two go hand in hand. But I want you to take a step back and look at this. This guy is following the rules (assuming he is interested) and look what he has you doing... You are thinking about him, a lot. Enough to ask the internet what it thinks. You are building him up in your head, making him seem better than he probably is.

Why call the next day if when you wait 3 days the girl he probably worked herself into a tizzy. Then when you do call a rush of calm comes over her as she stops worrying. Combine this with excitement and it is a pretty good feeling. Before you know it, she has associated feeling calm relaxed comfortable and excited with this guy, and all because he followed the 'rule'.

Granted, that is an extreme scenario, but it is difficult to argue with its logic. It takes almost 0 effort to do nothing, and if all you have to do is do nothing for 2 days to avoid being creepy or despereate and to be thought about a lot, they why not just play it safe and wait.

I know it sucks, but you can't blame the guy for it.