It depends on the airport, on smaller airports deicing is often done at the gate, for example EDDK, but on bigger airports there are specific deicing areas. During the last years, a lot of airports which didn't have deicing areas have build those. The reasons are:
- Faster deicing
- Deicing closer to the runway
- The possibility to collect and recycle the deicing fluid.
And yes, deicing areas are really needed, same als european deicing vehicles. Deicing areas are used in: FRA, AMS, MUC, DUS, PRG, CPH, OSL, LHR, YYZ to name just a few...