What constitutes an "emergency"? Dead stick? How much glide do you gain dumping ammo?
Regardless, dumping so they could fight better is how a ton of people would use it.
Wiley.
An Emergency that means staying inflight is difficult/unassured; fuel tank leak, oil leak, radiator leak, engine outage, large surfaces such as a blown off wing tips.
Depending on altitude it could be hundreds of yards, losing weight for a longer glide can potentially help a combat ineffective aircraft make a runway.
People already do similar by the use of Drop tanks, though the option of DTs are not available to all aircraft..
The ability to fuel dump would even that playing field, if you insist to go down that avenue of debate.