The .50 cal is heavy and needs a vehicle to carry it around unlike the compact, and relatively lightweight GPMG, but the venerable ‘ma deuce’ hits far harder at much longer ranges – 1.5 miles later your lead is still flying and your enemy is still ducking. A sustained burst of fire will shred a wall and stop most vehicles apart from advanced APCs or tanks.
Stick it up on a truck or even a Humvee and you have a truly powerful, mobile weapon for a fraction of the cost of other platforms.
That trusty M2HB is reliable as well as versatile.
It terrifies enemy infantry.
It can be used to range in your bigger guns on a target.
In a tight spot it can be used to take down a 20 million dollar, strafing aircraft just as granddad stopped bandits like the Focke Wulf 190 with it in WWII.
No GPMG is a good substitute in that role.
It has no circuit boards to fry in an electromagnetic pulse, no batteries to fail, and no guidance system to jam with electronics or a burst of chaff.
Even in our technological age there are few better ways to even out a fight than with a .50 calibre machine gun, a well-trained gunner, and a thousand rounds of ammunition.