Some people like to take the initiative. Other people prefer to be more passive, and let others initiate conversations.
If you're calling your parents frequently enough, they may not see the need to ever call you because they know you'll be calling soon enough anyway. Before they ever have time to think "Oh, I wonder what our precious child is up to!", you've already called and info dumped it on them.
On the other hand, maybe you only call them like once every three years, and it seems like they just don't care. Maybe they think you just want to be left alone and are trying to be nice. Or maybe they're just forgetful, neglectful, or somewhat self-centered. Maybe they're just really busy or kind of confused and completely lose track of time (I'm not even 50 yet and I'm already at the point where you just sort of blink and suddenly realize it's three months later). Could be any number of possibilities.
Only you really know your family well enough to know what their motivations might be. Any generic advice you get from people here will probably be wrong because we're all talking out of our asses and know nothing about your family.
"Wall of Text'D!"
--- oldskoolplayr76
"POwned again."
--- blight family