Why does this guy expect me to reply straight away?

So been messaging this guy. I respond in a Timely manner. He’s usually the one very busy. For example he messaged me saying he’s finished work and then asked if I’m free or working he messaged ‘?’ After that when he didn’t hear a response it had only been 20 mins.

on the other hand he sometimes is gone for hours. However he does always say why he’s been busy. I’m just confused why does he want me to respond right away?

Another example is he messaged me saying he missed me & then as I hadn’t recieved WhatsApp messages he text me saying you recieved my message not sure they gone through?

Why does this guy expect me to reply straight away?
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