...
Can't really argue w/ the logic, particularly for motorized vehicles the risks are much higher than simply a little inconvenience or perhaps worst scenario some lost revenue if one's a professional woodcutter, for example.
But, all the trimmers, chainsaws and the like I currently have (and, counting I come up w/ ...let's see, that's five I think is all) came from the manufacturer w/ no clamp and at least a couple have very little room for one. I think all are at least 10 years old and some are at least 20 (inherited from Dad) and I've only had the one line on the oldest chainsaw need replacing since I came back after six or seven years additional use on my part. Granted, of course, this is pretty infrequent use, but my experience for these small engines is that the manufacturers didn't use the clamp simply because it really isn't needed until time the line needs replacing anyway.
Again, for a bike or a boat or even a lawnmower I'll agree w/ you I'd not consider doing without. Part of the reason, of course is they typically have much larger lines than the miniatures on the really small 2-cycle engines. Wouldn't surprise me that larger chainsaws come factory equipped w/ clamps as well.
Extra line almost never is a problem on larger engines, either, of course. On at least one of the chainsaws I have, more than an extra
1/4" doesn't work because the direction it runs causes it to buckle and pinch it closed. (DAMHIKT :) (or how long it took to find the _obvious_ cause :( )