It's not, really, though. Not compared to, say, driving a car or cooking a meal, or the many other things people do each day. I think this myth that learning a new RPG system has to be a lot of work could do with some pushback.
For the car analogy to work, learning a new system is not like
driving a car. It is like
learning to drive a car. I don't know about Britain, but over here, you need to take a class just to get a permit, and you take a whole lot of practice before you just jump on the highway.
So, you are comparing, say, driving a car (playing a game you know) to, say, learning how to ride a motorcycle. Not the same effort there. Folks, don't just pick up new skillsets in an afternoon just because. If I want to go to the grocery, I hop in my car. I don't hop on my wife's motorcycle and just learn to ride as I go. Folks make an active choice to take on a new thing, and have to work at it - and the experience while learning is no the same as the experience once they have learned.
Note: I am not against learning new systems. I am for it! Every time I start a new campaign, I'm picking up a new system, and teaching my group! But, I am also for recognizing the extra effort involved, rather than dismissing or minimizing it, and taking due consideration to making that effort pay off.