Why do we need RDP, VNC and a variety of protocols in general?

Question

VNC

I learned about the TeamViewer program a long time ago and as soon as I found out, I immediately tested its capabilities. Then for me it was just mega amazing.
A couple of years ago I learned that Windows has a built-in Remote Desktop Connection utility, which also allows you to fully manage another computer, but on a local network. I was only able to test it the other day. I liked it (except that you can only manage it over the local network).
I started to google what is the difference between the built-in utility and Team Viewer, I did not find direct comparisons, but I realized that they at least work using different protocols, Team Viewer - http, Remote Desktop Connection - RDP.
Then I googled that there is also a similar UltraVNC utility that transmits data via the VNC protocol.
There was a question.
Why do they use different protocols?
I understand that each of these programs converts information from the computer server in a different way and transfers it to the client, but I think this information can also be transmitted via http, for example, commands, pressed keys, etc. via JSON, pictures like desktop in png/jpg. Why use a separate protocol for this?

Answer 1

First:
RDP != VNC, TeamViewer - since RDP runs in a separate session.
There can be several RDP connections on one server, they do not see each other's screens, their keys / mouse are transmitted independently, each in its own session.
Secondly:
http is the lower level protocol.
If you are somehow going to transfer keys over it, etc. - you will need to come up with your own protocol
over http Thirdly:
http is a text protocol, not binary. It conveys quite a lot of unnecessary information.
In order to ensure comfortable work through the network, to press a button and see a review - there is no need for extra links in data transfer.
Fourth:
http is not very good as a protocol for real-time two-way exchange (which caused the appearance of WebSocket).
Fifthly:
This is not so
. Sixth:
Well, let's all use the technology that was once invented.
Well, for example, to drive cars without pneumatic tires, with wooden wheels.
Many protocols arise:
a) as a process of improvement, as a solution to some additional unique problems.
b) some protocols, like the TeamViewer protocol, are closed and inaccessible to other developers.
But, for example, the same VNC (these are the only of the three TeamViewer you mentioned, VNC, RDP - an open protocol) - is used in different software. For example, in locally running virtual machines to connect to the console, or hosters to connect to the "local" console of the client server.
But in general:

Answer 2

зачем? потому что они создавались по этому принципу: https://xkcd.ru/927/
==
http не позволяет в полной мере обеспечить функционал требуемый программами этого класса хотябы потому что http изначально не умел держать постоянно открытое соединение

Answer 3

Еще есть X11 forwarding который родственник RDP.