Ideal pushing gear-ratios?

[Oblarg]

So, I've been doing a bit of back-of-the-envelop calculations, and it seems that for any drive geared for a top speed of under ~12 feet-per-second, a dead pushing match (i.e. comparable to pushing against a wall) is going to be traction-limited rather than motor-limited.

If this is the case, why is the spread of gear ratios offered on most FRC shifters so big? If you're already traction-limited in a pushing match, you're not going to be getting much utility out of gearing your robot to push harder. A 2.56:1 shifter spread will result in a drive that's set for 16 ft/s in high-gear having a low-gear which seems wastefully slow - does it actually result in better performance than, say, 2:1, or perhaps even less?

I feel that I'm missing something here. Note that for all my calculations I've been assuming a robot weight of ~150 lbs, and a wheel COF of ~1 - I am aware that the former is a bit on the heavy side, and the latter is a bit lower than what you'll actually get with plaction tread.