While it may technically be true that a cab has to take you anywhere within city limits, it seems to me that it is only polite to ask first before you ask to go

While it may technically be true that a cab has to take you anywhere within city limits, it seems to me that it is only polite to ask first before you ask to go someplace out of the way. On the occasions where I wanted to use a cab to go from Manhattan to Brooklyn or an airport, I always ask first. Most of the time, they say ok, and it's all good. Once in a while (maybe 1/4 of the time) the driver refused. I'm fine with that, you can usually catch another cab within a few minutes -- one who will be happy to serve you. These guys work long hours and I do not view it is as my right to force them to provide me with service. The law is probably a good one. That said, I believe a certain level of consideration on the part of customer would also be nice.