At 30K on the WR G2s on the XC, I haven't noticed any noise increase. They still ride quiet and smooth.
I've got 20K on the same tires on the MB, and they're still quiet and smooth...
So many factors affect tire wear and noise, it's hard to determine the precise reason they've gotten noisy in your cases...so far, so good in mine...
2016 Tundra Crewmax 4WD 1794
2005 MB S600 (90K, Michelin AS3, M1 0W40)
2002 V70-XC (218K, AltiMax RT43, Castrol Edge 0W40)
2002 V70-T5 (189K, IPD bars, Bilsteins, Contis, Mobil 1 0W30)
1932 Packard Sedan (straight 8, dual sidemounts, original paint and interior, Shell Rotella 15W40)