Hmmm .... I do see where the OP might be coming from. It doesn't sound as if the PIL's announcement has arisen because they've been put upon, and of course they are entitled to have fun. But you see, I'd have thought if they wanted to have fun they need to just get on with it - they obviously don't need to ask permission to do so. By making a stark statement like that, it does come across as rather a rejection of their children. If these adult children haven't been taking advantage, then why say it at all ? I guess I'd just personally feel a bit shocked that two people I imagined I had a close relationship with were telling me - in advance, 'cos they might not happen anyway - that they didn't want to hear about any issues or problems I might have in the future. That seems selfish to me .... and I don't think it's simply a question of having done "their bit", because to me, being close, and wanting to support friends and family (those I liked anyway !) doesn't have a time limit on it ..... basically, if I care for someone per se, I will care for them indefinitely - which would mean offering whatever support I could (emotional, practical or financial) if they needed it until such time that I was unable to do so for whatever reason (e.g. if my health restricted me) unless I did feel I was being used. In return, would hope that my concern/support/help would be a two way street and they'd do the same for me.
This scenario reminds me of "fairweather" friends .... who avoid you and/or disappear completely when you need a shoulder to cry on every so often. It's not a nice feeling at all to realise that your company is only required when everything's going swimmingly and your "issues" don't affect them in any adverse way. You see .... I think genuine friends, and hopefully close family would be regarded as such, accept each other warts and all. Life is very rarely smooth for all of us all of the time, and, so long as people don't take the piss, I actually get a certain amount of pleasure - if that's the right word ? - in being able to help a friend through a rough time if I can and they want me to. That can be as simple as being on the end of a phone line, or relieving the pressure on someone by doing their ironing. Don't get me wrong .... am not saying I enjoy other people's problems, am just realistic enough to appreciate we all have them from time to time and personally I'd hate to think someone I cared about was keeping stuff from me whilst struggling in some way. Yet this is what the PILs are expecting their children to do .... I don't think that's healthy TBH. They are effectively asking them to lie, by ommission, if they should ever find themselves with an issue or problem or alternatively, risk being very hurt and rejected if they share what's happening and the PILs say "we don't want to hear about it". It's not a case of adult kids being too dependent, and most of us would try to sort our own troubles out and worry our parents as little as possible - but there does come a point, depending on what's happening, when it can be impossible to pretend/hide stuff. I don't think it's unreasonable to hope that your own parents at the very least would express some sympathy and empathy, yet this pair have effectively told their kids not to bother them any more.
Not surprisingly - given my views expressed above, I have very similar experience of this. My own mum has never made such a bald statement, but her actions speak louder than words. Consequently, there are huge swathes of my life past and present she knows nothing about, because I know from bitter experience that I'd be rejected if I tried to share a trouble and hopefully get some sympathy. I can guarantee that if I even begin to talk about anything not quite "nice" - like the weather, TV, or kittens - that she'll make her excuses (lunch ready, someone at door, toilet etc) and that I won't hear from her again for months on end - and when I do she won't refer to whatever it was that was troubling me. It is incredibly hurtful .... you do imagine that your own mum would want to be involved in your life as much as possible and would care enough to manage a few sympathetic noises.
Sorry OP ... have rattled on a bit.