Lighting controls can’t make up for a poor design, but they can help a design go from good to great.
A good design starts with mapping out the lumens of illumination needed in the area being lit. The designer uses that map to determine what kinds of fixtures to use and where to install them. Note that the amount of light needed can vary within a given space.
If you need less light at some times and more at others, controls will allow you to meet that need. In a conference room, for example, you might want to reduce the lighting so people can view a projection and still be able to take notes. Dimming is a simple control frequently used for this purpose.
Dimming not only gives you the lighting change that you want, it also reduces energy usage. However, the limit to dimming is 20%. Below that, you lose the energy savings. You also put added stress on the lamps and ballasts, something that may even be audible.
But what if your application really needs, say, 15%? For a smallish room, one solution is to control some lights (e.g., accent lights) with switches and some lights with dimmers. For a large area, the best solution is a programmable lighting control system that changes lighting patterns according to the scene you select.
Dimming is only one control option. Plan your lighting system based on lighting needs, then look for the controls that will meet those needs.