Oh yes, I remember dictionary servers. Also many other protocols.
What happened to all of those other protocols? Everything got squished onto http(s) for various reasons. As mentioned in this thread, corporate firewalls blocking every other port except 80 and 443. Around the time of the invention of http, protocols were proliferating for all kinds of new ideas. Today "innovation" happens on top of http, which devolves into some new kind of format to push back and forth.
I wouldn't place all the blame on corporate IT for low level protocols dying out. A lot of corporate IT filtering was a reaction to malicious traffic originating from inside their networks.
I think filtering on university networks killed more protocols than corporate filtering. Corporate networks were rarely the place where someone stuck a server in the corner with a public IP hosting a bunch of random services. That however was very common in university networks.
When university networks (early 00s or so) started putting NAT on ResNets and filtering faculty networks is when a lot of random Internet servers started drying up. Universities had huge IPv4 blocks and would hand out their addresses to every machine on their networks. More than a few Web 1.0 companies started life on a random Sun machine in dorm rooms or the corner of a university computer lab.
When publicly routed IPs dried up so did random FTPs and small IRC servers. At the same time residential broadband was taking off but so were the sales of home routers with NAT. Hosting random raw socket protocols stopped being practical for a lot of people. By the time low cost VPSes became available a lot of old protocols had already died out.
What happened to all of those other protocols? Everything got squished onto http(s) for various reasons. As mentioned in this thread, corporate firewalls blocking every other port except 80 and 443. Around the time of the invention of http, protocols were proliferating for all kinds of new ideas. Today "innovation" happens on top of http, which devolves into some new kind of format to push back and forth.