It's most useful in such cases (and trams and so on), with very frequent braking and starts and a lot of trains. There is always some other train accelerating. And you have majority (if not all) axles powered, so you can have regenerative brake on all of them, allowing you to brake effectively only with the regenerative brake to almost zero. It's even much more silent than a mechanical brake, also an advantage in urban environment :-)

(And even if you don't give the energy back to the network and just burn it in the resistors in locomotive, it gives you more effective braking. Locomotives from 1960's already had that.)