True Pat. I often do the same sort of thing with curves but going on other forums a lot find levels easier to use. Might add especially beginners. It’s also adequate all on it’s own for many shots.
I agree concerning auto but on some shots it is worth running and may need each channel adjusting. I also think it’s easier to adjust individual channels for some of the situations that can turn up due to mixed lighting. That too can be done with curves.
I suspect the reason people find it easier is that small curve changes can make a big difference and also levels wont produce “odd” curves as it can’t.
I’m also pretty sure that you are a very experienced GIMP user. 
I follow your blog. Some aren’t. I think 2 posts cropped up that agree with my general feelings on the subject. I also think that anyone who stepped back from the fact that they can use curves effectively would also agree that it’s easier to use. Not so capable true but often adequate.
I don’t know how many times I have posted things like this along with an explanation of what it does. Usually to no avail. People don’t seem to have any problems with black points, white points or contrast using levels. Try telling them that this increases mid tone level contrast etc and eyes glaze over. It’s too much in one go. I mean by shifting the black I have kept the contrast. Eventually some then get to grips with curves.
