For the most part, I don't think it is a matter of 'sticking it in your eye' by not changing the signage. For the most part, I do think it is a matter of the Parks & Rec people not knowing the law, or not even thinking 'how does this new law affect our department'. In some cases, it might even be a matter of budgets (ie: 'We aren't scheduled for new signs until next fiscal year' or some such).
I know out where I work, the one community park's sign is out of compliance. I wrote a memo up the chain, to advise P&R of the change in law, and what the correct verbage should now be. I don't know how long it will take to get it changed, but I'll be following up in the next few months.