I don't ask, nor do I plan to.
I also don't ask about other threats to life and limb (powertools, explosives, poisons, pools, etc.).
If I'm letting my son go over to someone's house, I trust them to either keep hazards away from children, or children away from hazards. I don't trust *everyone* to do so. Which is why before I could reasonably trust my son, I went over with him. Now that I can reasonably trust my son, these are conversations we have.
Are weapons an attractive nusiance? OF COURSE.
Do I trust my son NOT to be around someone jumping in a pool unsupervised, handling a firearm, setting off fireworks, turning on power tools?
Nope.
But I trust him to pause. And I trust him to think about it. Which puts the onus on him and myself.
On him to pause.
On myself to know the people and their habits that I'm sending him over under their care.
In the case of firearms, that means that they would be appropriately stored, and wouldn't be handled without my permission. I DO have a short list of people I would trust my son to TEACH about weapons (for example, firearm safety, or hunting)... but those are the self same people who would -as a matter of course- have me there at the time or gain permission ahead of time and they'd be handled appropriately at all times. (ex military, current police, serious hunters, etc.).
I wouldn't mind if someone asked me. Currently I don't have firearms in my home, but I have. And may, someday, again.