If the risk management strategy of contacts involves having a pair of glasses on hand, why not jump straight to that (unless you don't like glasses in the first place and only use them if all else fails)?

Then again, my eyesight isn't bad enough for me breaking my glasses on a holiday to be a potential problem. I've never broken any of my pairs before, and even if they were lost, I'm still able to read and get around. It's just more unpleasant to do so. But I still prefer glasses and wear them pretty much at all times.

Before I got LASIK, I wore contacts but travelled with glasses. There are a huger variety of reasons that you might use contacts even if you have your glasses available. In fact, everyone I know with contacts also always has a pair of glasses that goes with them on travels.

In my case I worked onboard tall ships. Contacts let me be on deck in inclement weather without worrying about spray, fog, or losing a pair of glasses, let me use any pair of sunglasses instead of a ~$250+ pair of prescription glasses, as well as things like diving and snorkelling without needing a $150 prescription mask.

Try having vision worse than 20/200 and getting around without glasses. When I traveled, pre-contacts, I always packed a spare and a repair kit. With contacts, I pack one pair of glasses, a repair kit and spare contacts, its essentially the same prep and experience. Except now I have peripheral vision and can wear whatever sunglasses I have on hand. They also don't fog up like glasses do, which makes the transition in and out of buildings in hot, humid climates where AC is prevalent less annoying.

I've used contacts for about 20 years and I prefer them to glasses doing anything active and generally traveling. I would be very worried about navigating the world without being able to read things 3 feet away with my prescription of -4 so I always travel with a pair of glasses.