[I found this interesting and wondered if "just seeking workout opportunity" was a common practice. Then it got me thinking about those highly-skilled players from big org teams who came out to our mid-level (but developing) org tryouts. They would get every coach drooling, get offered a spot, only to say they're just going to stay with their team.
I say it's a good way to burn bridges, but then again ... If you're a highly-skilled, impact player, coaches can be pretty forgiving if you came back for that spot
I think a lot of these situations are driven by parents wanting to "show off" how great their DD is. Some of them are there to gain tryout experience which I think is fine. This all seems to happen mostly at 10's and 12's. I am sure that some players are there as a backup plan in case something changes with their high level team like another stud getting picked up at their position. I see this especially with pitchers parents that get all butt hurt when their high level team picks up another stud or two and all of a sudden their little flamethrower is #3 on the depth chart.
For the higher level impact girls, it seems once they are older in high school, they would rather stay in bed and sleep in than go to some tryout for a lower level team that they have no intention of joining. Either way, more experienced coaches will be able to sort through those players and not get to hung up on them.
As far as burning bridges... softball talent is a very thick bridge and it would take quite a bit (usually big mouth disruptive parents or total player disrespect) to burn it down when it comes to impact players, especially with the newer coaches. The ones that have been around for awhile will blow the bridge up pretty quick if the parents are asses.