Not always the case; some times our descriptions do not make sense in their mine they see something different had that happen several times
Or we simply don't want to spend 20 minutes describing every single feature of the room or area, and the players also don't want us to do that, and who even has time to plan that much detail out ahead of time, every time?
So, the players ask questions appropriate to the vague plans forming in their heads, and I answer.
Also, sometimes you describe things, and players don't have perfect short term memory. This is why I like drawing things out or using maps, but even then sometimes you can't tell/don't remember to draw everything, especially in a 3d sense. And we definitely play the game in 3d.
The "worst" I've seen with this, at the table, went vaguely like:
Player: How tall is the stairway, again?
DM:15ft, and it winds gradually, think ballroom more than tight spiral, to the south, here, ending in this area that overlooks the main room, with a rail about navel height to an average man.
Player: Ok, and do the rails up the stairway and on the landing look sturdy?
DM:<checks character's perception and investigate numbers, which in this case are quite good> Yep, not only that, but you've noticed in general that the place is in less disrepair than a cheaply built manor would be, abandoned so long. Unless I say otherwise, assume most stuff is still pretty sturdy, built to last.
Player: ok, sweet. I <describes what she wants to do, and how she wants to do it>
DM: Nice. Go for it. (it was pretty straightforward, and her description included what skills and features she'd be using at what points, all of which made sense with the game's action economy and other rules, except that she forgot to one aspect of jumping) You'll want a running start or some kind of vault for that jump, don't forget to leave enough movement in your path for that.
Player: MMMk, I think I'm good
<resolution of actions ensues, giant monster bear troll gone wrong thing gets rekt>
Her turn took a little longer than normal, but the payoff was well worth it.
Especially in 5e, which moves so much more quickly than previous editions, I just don't see the problem. I'd much rather my players feel free to ask questions in order to pull off crazy stunts and the like, than feel like they aren't "supposed" to interrupt the flow of the round to clarify things.