It's for shitsucking jackass pussyboys.
However, those shitsucking jackass pussyboys are also creating a real asset for countries that can't afford to take a moral stand. Sadism in this case is more profitable and effective than the losing battle against poaching. It's a tongue-biter. Useful and justified for a limited time only.
I'm not terribly convinced by this explanation.
Some countries do a good job of managing it and bringing hunters in for cash flow. But most of those wellmanaged countries have been increasingly shifting to non-hunting tourism (often while still maintaining some areas for hunters).
So a lot of those hunting trips, especially for exotics, happen in countries that have serious corruption problems. Those countries don't do much for conservation. The hunting doesn't help prevent poaching. The money doesn't go towards locals. Frequently, most of the money doesn't even go towards the government, except a tithe to corrupt officials.
Google tells me that one of the places Glass does a lot of hunting in is Zimbabwe. Zimbabwe's elephant population has dropped. Almost none of the money spent by trophy hunters in Zimbabwe goes towards preventing poaching or the local population (excepting some bribes). Most is paid to hunting guides, who are rarely local themselves. This should not be surprising, given Zimbabwe's problems with corruption.
By comparison, although Botswana does allow trophy hunting, it does not allow it for elephants. Yet Botswana still manages to fend off poachers better than most other African countries, and is one of the few with a growing elephant population. (It's actually boomed sufficiently that they're starting to be overpopulated in some areas.).
If you don't want to take my word for it, here's natgeo's, noting similar issues across a broader range of countries.
https://news.nationalgeographic.com...ng-elephants-tusks-poaching-zimbabwe-namibia/
Disclaimer: some friends of mine have studied or are working in the field and I've "safaried" in a number of the relevant countries with them.