Every player who plays with DM's who thinks that they're going to challenge them by not having enough waterskins. You might get away with that once, but, after that? Not going to happen. I mean, carrying half a dozen extra waterskins when preparing for extended overland travel is something your players never do? Never minding the mind blowing expenditure that is a horse or pack mule. Wow, I know right? That's just totally mind blowing that players might do that.

Of course, every pack animal will automatically be killed fifteen feet from the town gates, so, I can see why players don't buy them.
Like I said, the presumption that the players are actively stupid seems so far beyond the realm of reasonable. The other thread about exploration is just chock a block with this. It's the standard response as soon as any discussion of any negative element of 5e comes up. We're going to keep bringing up examples where the players are complete gaming newbies with a sense of self preservation akin to small flying insects hovering over trout ponds. It's so completely self serving and frankly it's really difficult to think that the arguments are being made in good faith.