Why are enemies so obsessed with walls now?

[BoogieMan]

I hadn't played in about 6 months, but I picked up ideology and started playing again. Now when I play I find raiders to be a bit dumb and a little annoying. Raiders, mechanoids, they are all obsessed with destroying walls and mountains. Even walls that are inconsequential and destroying them does not help them get to my colony from another angle. I can claim ruins and debris on the map and sometimes they'll go blow them up seemingly just for giggles. If the wall didn't exist, it wouldn't make any difference. I've watched centipedes blast through a mountainside about 12 tiles thick instead of walking through a little bit of water way at the northeast edge of the map when my base is in the extreme southwest corner. It would have taken them maybe 10 seconds to cross.

I can put a line of wall in the middle of the map 20 tiles long, that doesn't black access to anything, and everywhere to the left of this is a massive amount of thick walls, mountains and a wide deep river that would probably take them days to tunnel through to me. They will go down this wall blasting it down to take the extremely unfeasible and long way to me. Meanwhile, there is a narrow section of mountain to the east that they ignore unless the enter the map there. The path to my base is wide open with nothing to slow them down. They would rather bunch up against the mountains and kill each other with grenades and try to tunnel through an entire literal mountain instead of just come at me or at least be slightly sensible with their aversion to even standard barricade/turret guarded entrances. It's like it is utterly inconceivable to just come for a strait up fight which is more fun than always hitting them with mortars while they're friendly fire themselves with grenades while bunched up against a mountainside.

Does the game just always want you to mortar them or run out into costly open field battles and just not use fortifications and turrets now? Because that's what it feels like. When they mad rush my entrance they at least have a chance to hurt my colony. But crowding up and letting me wreck them with mortars accomplishes nothing. But it's their preferred strategy.