Well, I think the problem is sometimes you can't get your hand on them very well. At least in my case. Also, even if you can get at them, the larger ones like 1.5" are pretty tough to tighten by hand IME. Also depends on the glass thickness - I can't imagine breaking the glass on my 180 but a smaller tank with thin glass would break pretty easily I'm sure.
I usually use a rubber "strap wrench" - I don't know their real names, but you can get them at Home Depot, Lowes, Harbor Freight, etc. They work OK but not great when things get crowded.