It matters because to disregard Zoro and Usopp's pasts just because there were over 1,000 chapters ago and not the same as pasts like Nami's pasts might be setting the bar a little too high, with all due respect.
If you really don't think Oda's standards for how to construct a crewmate flashback changed over the years we'll have to agree to disagree. If people got Zoro and Usopp-level backstories for a new member, they would be rightfully disappointed. Yamato is still above that, of course, but I still think it's disappointing compared to all of the others and I really didn't think that would be controversial if he is to become a crewmate.
I don't know dude, sometimes this thread feels like a battleground where you have to pick a side and disregard and dismiss any points made by the "other team". It just gets tiring.