There's a lot of people who don't have their parents anymore, and wish they did a little something for them when they turned 50, 60, or 70. If you're going to have a party for them at those ages, especially 70, then it should be something formal, and during the daytime, in the style of a banquet...this is if you have a large family, and you're inviting extended family members, by sending out invitations. They'll talk about it for years, especially if that was the first party they ever had. But by the time they're 80, and although they've reached another 10 year milestone, they usually don't want no big birthday party. Taking them out to dinner would be ok, or maybe throwing a little something on the grill.
How is being in your 30's, even your late 30's, too old for birthday parties, especially if they're not still having them every year. It's not out the ordinary to do a little birthday party when you reach another decade, especialy 30, 40, etc.... But like I said, 80 is usually the cut off point for celebrating with a big birthday party, probably even if they never had a birthday party.
I remember everybody was having a 50th birthday party. I wonder whatever happened to that.