The figures are only for devices with market access, so most tablets won't be included.

the significance is that developers will be targeting the largest market share (which is 2.1 and above), so few applications will be written which will be compatible with android 1.6 and below.

If running apps isn't necessary then an update to Froyo is less important. there are a number of features (like installing apps to the SD card) which were introduced in 2.2, but again without apps being developed there is no need of this feature.