I recently encountered a small Hilton washcloth towel at a rental unit in a part of Europe where the nearest Hilton is either a few hundred miles away or even two or more countries away. But this kind of pilfering is not the reason why some Hilton hotels are low on some towels at times. Some Hilton hotel owners/managers have gone to reducing laundry volume and costs and as part of that have been disappearing some things that used to be more common than they are now and have been trying to reduce their costs for getting laundry done.
The more private equity involvement there is in a market, the more likely this kind of thing happens. The more that other hotels do this kind of thing, the more likely other hotels jump on the same bandwagon too. Rat race to the bottom is in full swing in the US hotel industry, and it's the customers left paying more while getting less because of it.