I've done it many times.
If the foundation in a basement comes up too high, you may not be able to mount the panel vertically and still meet the top breaker's height requirement of 1.7m, without building out a wall...
And the odd service upgrade. If the old panel was sideways, then often the new one is too. Branch ccts can fit right back where they were. ETC.
I've only ever been asked WHY? once by a customer. And the foundation/breaker height was the reason.
Subpanel feeds don't need a guard, so I get happy when I can bring the feeder cable in anywhere at the panel. It's like a friggin treat for me.
I like and dislike the guard rule...
It can be a drag for fishing into the attic when the main breaker is at the top. No branch ccts allowed through there. Or down when it's mounted down.
But it's nice to have that area sealed off when I'm tying in branch ccts. Hydro doesn't have a breaker that I can reach to turn their service off, so the guard is nice.
Though I think it can be important to have a hazard near by that can bite, then you are always careful. Careful skill.
Either way.