Why doesn't anyone take orcs as prisoners?
It struck me that being taken prisoner is a central point in many Tolkien plots - Frodo at Cirith Ungol, Merry and Pippin by the Uruks, Gollum by Aragorn, various imprisonings by Morgoth... and there's no mention (as far as I can recall) of orcs or uruks being taken as prisoner. A lot of it ties to the "fundamental evil" question regarding orcs for sure, but it is still a bit bewildering. Prisoners have since the beginning of time been an invaluable source of information, as well as being able to exchange for prisoners from the other side (this of course is a bit more irrelevant in Middle-Earth and the cruelty of Evil towards their own subjects). Similarly, the medieval and classical history and mythology that Tolkien drew upon often includes taking prisoners as important events.
Indeed, the Dunlendings that surrendered at Hornburg were shown mercy, but they were in effect prisoners of war before this. So the forces of Good do take prisoners, simply not orcs. Given that there are orcs and uruks with more operational and tactical knowledge (such as Ugluk, Grishnakh, Shagrat and Gorbag) that could be of use to military planners of the Good side. Yes, the common orc perhaps does not have much info they can give yet we know that even regular grunts can betray a lot that they do not even know they're giving away if you get them talking - there is plenty of rumour about military operations that is being talked amongst orcs in their downtime. And I do not for a second believe that all orcs and uruks fight to the death - the sheer amount of non-lethal yet incapacitating injuries that fighters sustain on the battlefield makes this impossible. There have to be many orcs and uruks still alive in the end of engagements between Good and Evil forces. So why not interrogate them? We know the Evil forces to do so constantly.
(As an aside: I always thought it a bit odd that the raid on the Haradrim convoy conducted by Faramir did not score any prisoners - surely interdicting an enemy convoy would entail getting a few "talkers" to possibly gauge the strength, intentions, timetables et al of the enemy. And don't tell me the Palantir is a get-out-of-jail-free card when it comes to military intelligence - not only is it not and Denethor, even in his pride, would not completely rely on it, the captains on the ground would still seek to operate according to common wisdom which would surely be to take prisoners for interrogation)
I would wager the reasons are many, both in- and out-of-universe: that perhaps they were indeed taken prisoner and Tolkien simply neglects to mention it; that Tolkien wished to avoid the subject in its entirety because of either the logistics of interrogating orcs or of the implicit cruelty of murdering all survivors of a battle instead of imprisoning them; that perhaps there was indeed a fury and distrust strong enough towards orcs that standing orders or a cultural standard to not take any of them as prisoners was common. But it still stands out as an odd black hole, unless I am missing something (which of course is entirely possible).