Most people don't differentiate between this certain difference:
Keybinds: Perform a
singular action, usually replacing that of a keyboard key.
Macros: Performs
multiple actions that replace that of many keyboard keys.
You do not need to have the macros mod to have macros, there is software available to download free. The majority of it comes with keyboards...
The reason that it is not allowed is because it creates an unfair advantage, people with macros can do an action in a shorter timespan, automatically. eg switch to fns, place it, and back to sword in a fraction of a second. Key-binds only replace something that is accessible to everyone and make it a small amount quicker, dependent on where you have your bind. As for the client-side macros mod, mods used to use it to save valuable time in warning chat offences. Staff members are not allowed to use it for game-play features, it is almost always used on MCSG for it's custom GUI function - a window pops up and you just click what you want to post in the chat. Hope this helped