A lot of times those parents have contacted the coach and asked them to come watch them.

Especially this time of year. I get contacted all the time by parents wanting to tryout for our team and asking me if I can come watch them ahead of time. In Plano, last weekend, I cannot count the number of parents who came up and asked me to watch their kid and see if we would be interested in her trying out for us next year. If I am approached by the parent, I will look at the kid. If not, I may watch them, but am not going to try to find their parents and recruit them. If your team is good enough, they know who you are and we want kids who want to play for us, not kids we have to try to talk into it.
Now, there are some coaches who never stop recruiting and will try to recruit your kids while playing against you. I always tell them, please just tell me which kids you want and I will be the first one to encourage them to go to your tryouts, the last thing I want is a kid that doesn't want to be on our team.