I've seen a few people using these (or similar cheaper/flimsier housings) on recent trips. I totally get the appeal given the convenience and minimal cost of entry, but if it were me I would be extremely hesitant to put my cell phone in the water on an overseas trip, much more so than my multi-thousand dollar camera setup. If you screw up (flooding is usually user error of some sort) or something breaks and you flood/kill your phone you're now travelling with no phone. If I flood my big expensive camera there's no impact to the rest of the trip (other than the photography), and I make an insurance claim when I get home. Nowadays everything is digital. Itineraries, tickets, banking, contact info, etc... For a lot of people it could be their only means of internet connection. I suppose one could use a laptop or tablet for this purpose (if they had one with them), but it's certainly much less convenient. Seems not worth the risk in my opinion.
I will note that one of the guys I saw using one of these this year in Fiji had a second phone with him explicitly for underwater use, but at that point I'd question why not a gopro or something else cheaper and purpose built. Curious what everyone else thinks. Maybe it's just me since these seem to be very popular.
Note, this is not criticism of these housings in particular, which appear to be higher quality than many others I've seen.