For football sometimes I get there early to watch the end of practice. But usually more to BS with a couple dad friends. We have a 40 year veteran coach with a track record of success so he is not as insecure as some. Don't know what I will do when baseball comes. Depends on the dads! It's my only form of social life! Basketball doesn't lend itself to that so of course it's just drop off and wait in the warm car at pick up time.
But when I coached I always invited parents to practice - even for basketball. Invites them to sit by the dugout or bench if they like and listen in and routinely invites parents to post game talks. I just think sometimes coaches have to get over themselves a little. What you do shouldn't have to be too secret - and if it is as a parent I would really have to ask why. Long before I had kids I always told the parents "I shouldn't be saying anything to your kids I wouldn't want you to hear". As a parent now I feel even more strongly about that. Coaches would be well served to be a little more humble. This idea that they know it all and parents are idiots - and believe me I have known a lot of coaches like that - is just wrong. Sorry just a pet peeve of mine. Anybody who wants to watch their kid practice there's nothing wrong with that - however we have to live in the real world and since there is a stigma out there about it you may want to think twice.