The reason why killboxes exist.
Also a topic on progression!
The reason WHY killboxes exist and why everyone does them is because of ALL of the game's mechanics, not because "these STOOPID builders don't know how ELSE to get kills!"
Not being able to move GenMat favors bases that are close to the ground, or ones that go underground, which also limits types of bases that can be done.
Raiders, at basekit, have grappling and excellent movement. The grapple can be spammed, you can remain in the air infinitely, you gain extra speed when grappling, etc. The more open a base's rooms are, the more room the raider has to dodge, which allows them to remain in LOS of your traps and buy time to shoot and disarm them, ruining setups that costed a lot of capacity to make. You can place more traps and guards to counter that... but then that makes a killroom. Which is a biiiiig no no and "not fun for the Raider".
Raiders also have the permanent shield upgrade and seemingly easy to restock consumables that create barriers. Which prevents the "clever traps that all Builders should go for instead of killrooms!" from getting a kill on a bad Raider who deserved to die. Which is, y'know, never acknowledged.
Raiders also have turtling and speedrunning at basekit which shuts down traps and guards unless they're clustered together (aka a killroom :>), because Builders with no upgrades, guards or traps beyond the basic ones is garbage (which nobody acknowledges in the common "valid popular complaints" topics), can't do setups that will throw off raiders as a result, and trying to get smart with the base blocks is easy to see by a turtler and easy to react to by a speedrunner.
Just turn the corner and fire at the trap, there's several seconds before ANY trap goes off. If you see multiple, just move backwards, there's noooo way to consistently punish going backwards without some complex setup. Traps have garbage detection and are too slow when firing (favoring killrooms as a result)..
Oh and, the "put a guard outside the base and wait 30 seconds" trick doesn't work consistently enough to merit planning around because of the currency tombs. Which the community thinks they're entitled to, and the devs seem to agree. (lmao) If people go for tombs, that messes with the time that the guard needs to go in the entrance behind the raider.
Kills are also a note-worthy amount of a base's progression, being 50% of it, accolades are also optional and people typically give "Fun" if it was easy for them in my experience, and based off of the other topics, you will most likely need upgrades to be considered "Brutal". Same for "Ingenius". Raider? Not at all, of course. They don't have to do aaaaany of these. "Artistic" is great but I want to be lethal as well.
So, what do we seem to get? We get tight, packed rooms stacked with traps to halt progress, and other traps to prevent easily destroying said traps. Turtlers can't pick off traps one by one, and speedrunners will die if they go through it. Dealing with the room is difficult, and raiders will most likely die trying to do it.
But, y'know, this is a killbox. And of course, nooooobody likes playing those, don't they? So naturally, instead of changing Builder progression, the GenMat placement, etc so other types of rooms are encouraged, we should... let Raiders pick and choose what bases they want to do. Because "Builders should be using THEIR BRAINS to deal with my AMAZING skills and MY TIME IS VALUABLE!!".
And to address a potential rebuttal, let me flip some popular reasoning used in both DBD AND this community in regards to dealing with killboxes as Raider back at you: I shouldn't need unlockable traps, guards and add-ons to deal with basekit grapple and basekit Raider strategies, I shouldn't need to spend 5 hours cogitating over a base, thinking of these amazing, unforeseen setups to get invalidated by a single ######### shield. I shouldn't need to spend 50% of my capacity making a single setup to encourage actual thought, I shouldn't need to be restricted to dark, boring, ground bases instead of being able to make a cool sky base instead, where you have to parkour from isle to isle.
This is all why I haven't logged in quite a while, and only put in... 11 hours total. Which seems to be more than enough to get an idea on how things are. :)