I rarely find I use curl's -s without its -S, e.g. -sS. It seems curl's design is flawed in its definition of -s; perhaps it's historic and it was too late to change it.
The junk goes to stderr, so it won't impact anything but your screen when used from the command line. And sometimes (large transfers) you want that information. I think the default is sane. When you're using curl in a script you use -s, when you're using it interactively you want the diagnostics.
Yes, sometimes when it's a particularly large transfer I want a progress meter but I normally don't so it's in the way; perhaps when we all had modems. And from a script I'd still want to use -sS instead of -s because although the script is obviously checking curl's exit value the user wants to see curl's specific complaint before the script's own knock-on diagnostic.
