The color seps for all of the TPBs DC puts out are already paid for in recent printings - Archives, the recent comics themselves, etc. To convert B&W works to color reprints would require new work on something that is already marginally profitable, likely dooming it if much at once. That said, the B&W art does likely provide an easy seque to themed collection where 60% if already sepped. They can then do a little bit of work to color it and round out a themed collection. This then lowers the amount that needs to colored for a serial collection and back again.

I agree that time will cure all these ills. It's just the challenge of having 70 years of material available in the time we are alive is daunting.

D.