People who start a radio call with "And" are either a bit older or trained by someone who is a bit older. It was used back when there was about a 3 second pause between the time you pressed the PTT and the time it actually transmitted, "and" happen to fill that gap nicely, so the "and" was never actually transmitted. Nowadays radios have come along way and so people who are still use to doing it the old way will say "and" out of habit, and it will be transmitted.

The other reason for "and" is because the person does not know what they are going to say yet, it acts as a vocalized pause much like "uhhhh".