Actually let me change what I said - the point of ECM isn't to sneak up on guys and ruin their shit. That is, however, perhaps the most useful application.
Strictly speaking, given the way ECM and the probes function, they're designed to support long-range combat as much as possible. You don't have to worry about sensors seeing through ECM at super-long range, whereas in brawlers, you never really know just how close you can get before you're fapped. The entire point of probes is to see farther and lock faster. Really it's all geared towards that.
Still, ECM's most practical application is still the brawlers. IMO of course.
Changed my stance on this after reading and old post from Brainwright (basically saying the same thing).