Both half-life and half-life 2 require it's use.
If a map "trained" me to use jump-crouch, I'd probably be insulted - it's that basic.
By training I meant a series of puzzles to teach me - the 'press ctrl to crouch' is already in portal. That's all the teaching a player needs.
It's also very useful in Counter-Strike and Team Fortress.
i agree "shift to crouch" IS all the training one needs. HOWEVER its not in portal, and portal very well could be the FIRST AND ONLY game a person has ever played, not likely, but possible. not. the reason its not trained in portal is cuz its not needed. anywhere. so. thats all i'm saying. atleast one little ledge, that the ONLY way to bypass by jumping and crouching should be in a map (or atleast the first of a series of maps) if that mapper expects a person to know how to do it.
There is a entity in Hammer where you can disable auto crouch jumping as far as I remember, so I presume that simple crouchjumps are done automatically but not in all cases.
In my maps, I tend to not use it at all. Because, as rellikpd said, I saw people playing a Valve game for the first time with Portal, and crouch-jumping is not as obvious as we think. Personally, I try to extend edges with little platforms to avoid 128 units jumps.
If you want to talk about HL1, the tutorial even made you do it. Anyone remember the tiny tunnels?