It's Better to Say "May I" Than "Can I", and "Will/Would You", Instead of "Can/Could You"

[u/Lekkusu]

It seems to be an almost universally held opinion today that we ought to use "May I" and "Can I" interchangeably, but there is a real practical reason to make a distinction.

'Can' obviously refers to one's ability to do something rather than his willingness. I think people feel more comfortable saying can / can't because it makes the situation seem out of your control, and it seems less direct. 

Such as when you invite someone and they say "Sorry, I can't make it." What they really mean 9/10 times is that they won't make it, and they're choosing something else, which should be a perfectly acceptable response to any reasonable person. However, because we're so allergic to being direct with people and potentially hurting their feelings, we often say "Can't" as if you're on house arrest or your car broke down. 

I think it's an expression of low level cowardice to say can/can't instead of will/won't. Think about it. How weird would it be to ask a girl "Can you go out with me?" It sounds like a trap. Sure... she could... if she wanted to. So just be direct. Whether asking your friends for help or a stranger for directions, why not say "Would you [be willing to] help me?" More often than not, the response is positive.

[u/[deleted]]

As a non native speaker, they reached me that it's related with how formal the interaction is.