Comment by alerighi

It's not a matter of being afraid, spaces in filenames are annoying.

I mostly use the shell and navigating in directories with spaces is annoying, you have either to quote it or put a \ before each space. You also have to remember to quote everything, and in bash that can become complex, you start adding quotes everywhere to solve problems caused by spaces (or other special characters like *) in filenames.

So I prefer to not use them, a simple _ is as readable as a space. Only thing is that spaces gets rendered better on graphical file managers, but... that could have been solved (and can still be solved) by simply adding an option to render a _ as a space graphically if there is no ambiguity. I don't care that much since I don't use graphical file managers that much.