[atul]

Asking a NAP from a neighbour is a bit like asking some girl to a date in one regard:

No answer is an answer, and also it tells you that the one not giving you any answer is either just impolite, plain jerk or doesn't care enough to answer.

You can stall with other ways, or give very polite denial. You know, actually communicate.

Of course, cultural variations exist. I've run into some with foreign (to me) dominions players, with people preferring not to give a "no, I won't" answer in any situation, claiming they actually can't. And afterwards proving with actions they actually could have, just didn't want to. Which, to me, is the way you treat a child, not another adult. But apparently is "polite norm" in some places. Had a quite long conversation about these cultural differences a while back.