It is personal information so not everyone wants to spread it around, nor do some feel happy when someone tries to make them feel bad about keeping it to themselves. It's a personal decision.
As for what I think of my age, not a lot. I'd rather not have the aches & pains, the feeling of rushing downhill towards my departure, I'd rather a return to sleeping well, feeling well, having some enthusiasm for something once again. When I was a nipper I thought I'd be good as an older person, but I find I don't take to it well at all. It's just a continual erosion of everything one was once able to take for granted. And no I don't feel happier because plenty of folk are worse off, even if they do grin their way through it.