There are a more than a few factors to this question, but i'll give them my best shot...
The next factor is a supers approach to maint. Many times I see supers who perform horticultural tasks because of a date on a calendar or because that was the way they were taught. One of the nicest changes of pace I have been lucky to be part of is having a super who only does things when they are needed. It allows him to have more of the secondary items he would prefer due to savings from manging the condition rather than managing for condition. I hope that makes sense.
Jim, think you hit the nail on the head there in respect course management. There is a tendency for letting education over ride common sense. i.e doing something such as coring the greens because its on the annual maintenance program even if the greens don't need it, etc.
With regards to firmness. Looking at it in its simplest form it depends on two major factors. 1. Drainage. If the site is poorly drained then the ground will be soft after it rains and remain soft as the water can't get away. It is therefore important that suficient drainage that is deep enough (deeper the better) be install to deal with the seasonal needs. Surface drainage is important to deal with short term needs but can not replace deep drainage.
Added to this a program of slit aeration of all parts of the course from the semi rough in on a up to monthly basis and twice monthly (which can include slit, star, micro, verticut, etc.) will help greatly with surface drainage, rootgrowth and thatch reduction.
The second point is grass selection. You need to avoid thatch forming grasses going rather for the deeper rooting types. i.e fescue. The man made grass types such as Agrostis palutris (A-4, L93 and so on) create considerably more thatch if both sward types are correctly maintained. Too much thatch in addition to creating a softer playing surface makes the sward less drought tolerant. This inturn leads to over watering to keep the supposed quality of the sward high.
I would like to make clear that this is a very simple way of looking at it and it depends alot on the climate.
Oh and ryan does maintaining firmness cost more money. No, it should cost considerably less if the basic ground requirements of drainage are met.