99% of the time, they just want your money.

The fine (usually $15 for the ticket and $185 in court cost depending on location) is intended to sting you a bit and get you to slow down and be cautious for the next few months, while they get some cash in their pockets.

If it was a speed trap, and you weren't doing anything ridiculous (sounds like you were not), and you were polite to the officer (sounds like you were), then you'll get to court and they'll offer you deal: pay the fine and we won't put points on your license.

In fact, depending on where you are, you may be able to pay the fine online without even needing to go to court, which is what I did when I got one in Wake County.