There's probably a lot of truth to this, and I use my own houserule initiative system*, but even with RAW initiative, I get the impression often that monsters/NPCs can't interact with the environment around them unless it specifically states so in the statblock. For me, that's half the fun. That's how you end up with swinging from the chandalier, flipping tables--all the heroic actions from movies. Why can't the ogre kick over his firepit at the PCs, creating an obstacle? Why can't the goblins attack the rope bridge, forcing the PCs on it to make DEX saves? Why can't orcs form a phalanx of pikemen in front of the orc archers? Why can't the ogre grapple the PC and throw him into the alligator swamp? that sort of thing.
I think it's because cyclic initiative and the format of the MM causes people to start thinking in board game terms. They're no longer thinking, "Oh, this is an ogre who was in his home with his ogre buddies eating a rotten cow five seconds ago and is now looking at a bunch of heavily-armed ugly humans who just kicked down his door." They're thinking, "It's my turn to Attack/Dash/Disengage/etc."
The kicker is that I think it's really quite difficult to think in combat turns and also think in roleplaying terms. It's natural to say, "Oh, this ogre grimaces at his ogre buddy and then they each pick up one end of the table and hurl it at the PCs," but because that quite-natural interaction is complicated when you translate it into discretized combat turns ("I grimace at the other ogre and Ready an action to hurl the table as soon as he does likewise"?), it is no longer a natural thing to do if combat turns are your basic unit of interaction. And I think that can easily bleed over even into actions which
could be expressed as a discrete action, like "I grimace at my buddy and then throw a cow head at the humans" because combat turns bias you towards thinking of each character/monster in isolation, with everyone else being frozen in time until your "turn" is over. It's no longer natural to grimace at your buddy unless he can roll his eyes appreciatively or grimace back.
It takes a fair amount of mental sophistication for a player or DM to translate "take combat turns separately" back into "all of this stuff is actually happening at the same time, and the isolation is just a formality, and you guys are grimacing and interacting with each other throughout." Those who haven't fully internalized that sophistication will tend to steer themselves into action declarations which make sense in discretized combat turns, especially the actions that are
designed to be taken during combat turns like Attack/Dash/Disengage/etc. "It's my turn" doesn't mean "it's my turn to do anything," it means "it's my turn to choose from a list of things that can be done in a single combat turn." When was the last time you saw someone playing with cyclic initiative declare an action that would take more than one combat turn to resolve? "I'm picking the lock." "I'm still picking the lock."
Coming from AD&D, cyclic initiative is the worst thing about 5E, and the thing I'm gladdest that I fixed.