It's obvious. Someone clearly ordered 30 Reliant class ships to take light duties away from the larger more adaptable vessels. Someone mistook a smiley face for a zero and they ended up with 300.
So now they're just trying to wear the damn things out!
And really, that's the only reason why Starfleet keeps going to war. The Dominion? C'mon now, the war wouldn't have happened if the Federation didn't keep butting into sovereign territory
Consequently, what ship is most often seen on the front lines? That's right, the Miranda. And some of them *still* survived the war. Boo-yah!