I don't use Metafilter as often as I once did, so it's easy to forget how many little gems are buried in its comment strings. I'd never seen this one before, though it's something of a classic from what I've gathered from other web references.
This is a classic case of Ask Culture meets Guess Culture.
In some families, you grow up with the expectation that it's OK to ask for anything at all, but you gotta realize you might get no for an answer. This is Ask Culture.
In Guess Culture, you avoid putting a request into words unless you're pretty sure the answer will be yes. Guess Culture depends on a tight net of shared expectations. A key skill is putting out delicate feelers. If you do this with enough subtlety, you won't even have to make the request directly; you'll get an offer. Even then, the offer may be genuine or pro forma; it takes yet more skill and delicacy to discern whether you should accept.
All kinds of problems spring up around the edges. If you're a Guess Culture person -- and you obviously are -- then unwelcome requests from Ask Culture people seem presumptuous and out of line, and you're likely to feel angry, uncomfortable, and manipulated.
If you're an Ask Culture person, Guess Culture behavior can seem incomprehensible, inconsistent, and rife with passive aggression.
[by Metafilter user Tangerine]