I mostly agree with your point: keyboard interfaces are often harder to learn than the standard graphical mouse interface.
But I'd like to argue that a mouse also takes a bit of time to grok when you first encounter it. A simple interface like "each thing on the screen has a two-letter code; type the code to select it" doesn't sound intrinsically harder to explain to me than teaching someone how to use a mouse the first time. Especially when you consider that there's often a lot of subtlety in when to use the right or the left button. I find this is something that often trips up people that are encountering a mouse for the first time.
But I'd like to argue that a mouse also takes a bit of time to grok when you first encounter it. A simple interface like "each thing on the screen has a two-letter code; type the code to select it" doesn't sound intrinsically harder to explain to me than teaching someone how to use a mouse the first time. Especially when you consider that there's often a lot of subtlety in when to use the right or the left button. I find this is something that often trips up people that are encountering a mouse for the first time.