To change the speedo gears is not too hard or expensive, I think, but most people don't bother? I'm running 31's with the stock gears that came with my used transmission. My speedo reads about 10 mph under the true speed. In other words, when my speedo reads 60 mph I'm actually going 70 mph. I live with that with no loss of quality of life.

'89 4runner SR5, 3.0, auto (fun)
'93 xtra cab, dlx,3.0, 5spd (work truck)