They're cheap, and what I use for everyday life anyway. Luckily my short-sightedness is only moderate & I can find my way onto the boat without them so if I lose one or both in the water, no problem. Actually, even with a flooding mask, I have only ever lost one contact at a time, never both, so I'm still in a better position when I come out the water than I would be taking off a prescription mask
I admit, doing the mask clearing & swimming without the mask for the OW was fun - but luckily I was the only student and the instructor suggested I just keep my eyes shut and hold on to him as we swam ;D. If I lost my mask for real, sure, I'd keep my eyes open, the contacts aren't worth worrying about.
top tip for diving with contacts - even if you normally use weekly/fortnightly/monthly disposibles, invest in a couple of boxes of dailies just for diving. They'll last 30 dive days if you don't lose any - and the loss is smaller proportionally if you do. Particularly handy on a liveaboard or long trip - it cuts down on the weight of solutions, and feels more hygienic in tropical water which has a nice temperature for cultivating bacteria.
Finally, modern contacts, soft at least, can be worn for extended periods with minimal discomfort - even the ones not designed for sleeping in. If I'm ever unconscious long enough to worry that the contacts might have hurt or even irritated my eyes, frankly my contacts are the least of my worries.