PGA step, why small step is needed?

I see that some RF and IF PGA (programmable gain amp) have resolution as fine as 0.2dB use in application such as DVB-T. I wonder the need of such fine step. Why such a fine step is needed? What is the purpose of this?

Using available parts? For a receive only application, you shouldn't need AGS steps better than 2 or 3 dB, fading is going to be bigger than that.

Dave