Especially in the US, deer are extremely destructive to any environment they appear in, with herds numbering hundreds of thousands and eating every crop they happen upon. They were allowed to grow that much, partially because we have killed their natural predators, but also because hunting them has been aggressively frowned upon for decades now. So any suggestion of culling the herds is immediately and fiercely met with groups protesting any sort of hunting, without offering any sort of alternative solution.
My understanding is that yes, rangers can cull down the population, but it's actually not a bad solution to issue say $500 permit to hunt deer(that allows you to shoot say 2-3 animals), and that way you cull the numbers without engaging already thin group or rangers.
But the issue exists no matter who does the shooting - there are groups who protest any kind of animal shooting, even if their population is wildly out of control.
It's better to take payment for a license granting the privilege of doing a job, than to go through the rigamarole of hiring someone to do it, paying them, and keeping them paid even if there's no work for them at the moment. The reduction in payroll expenses, plus the license revenue, can then be invested into conservation-related projects. Plus, as fun as hunting may be to those who find it fun, many such people have other skills too, and wouldn't want to stop honing them just to be paid to hunt.
