I suspect that the (vast?) majority of people who travel that much don't check luggage regularly. The exception being people who need a lot of gear for whatever purpose they're on the road for all the time. Personally, I'm on dozens of flights a year and I only check luggage for a handful of those flights.

Anecdotally, luggage does miss connections on a fairly regular basis and if there are airline changes/international flights involved, it may take a few days to track a bag down. But I've never had a bag lost permanently and I can't remember the last time I've heard someone I know complaining about that happening. I think my parents in all their years of travel may have lost a bag permanently once.

ADDED: The statistic in the article doesn't really say what percentage of luggage is lost though. The quote is “Less than one-half percent of bags are ultimately unclaimed." So this is the case where they have the luggage but can't figure out who the owner is for whatever reason. Presumably other bags are just lost--probably most typically stolen.