Why haven't more people attempted to create chat/IM clients out of e-mail services?
Some weeks ago, I've come across Delta Chat, whose main thing is "(near) instant messaging using your email"
That left me thinking, has this been attempted before? If not, why? Also, why (besides servers' limitations as means to fight spam) isn't this solution used more often, given that e-mail has been a decentralized solution for well over 40 years now?
If you've ever looked into email protocols you'd find it's a nightmare of cludged together solutions piled on-top of each other over decades. It simply isn't designed for instant messaging.