The screen real estate isn't particularly precious on a desktop / laptop with a large, high-resolution screen (much less precious than mobile, for sure), but I also like to get rid of menu bars, tool bars, etc. just because they're visual clutter, and like you say, a keyboard makes up for them.

Ironically, I do enable them on my tablet, because I don't always have a keyboard attached to it. Tablets generally have enough space for full menus / toolbars, and lacking a keyboard they're arguably the form factor most in need of them.