What does your backstory mean at your table?

This one is not about any incident I've had, and I may not reply to everyone like I usually do. But more than once on this forum I've been told, and seen others told.

"Nobody cares about your backstory."

Are your tables so dramatically different from mine? My backstory shaped the campaign I'm in currently. I presented the idea as a future character since I regularly play with the DM and the made a campaign based on that idea. The other players are heavily tied in too. The campaign could not be done with any other character.

So what do you do? Do you just leave it in the background forever? Only take tiny bits? What's the point? How long are your backstories? I'm intrigued at what happens at other tables where "no one cares". Because I care about my fellow players and they usually care about mine too.

Is it just playstyle differences? Is non-involved player backstory that common?