As I understand it, matching revs makes for smoother shifting and reduces wear on the clutch plate. It also prevents a weight transfer from shifting, which is why Nissan did it in software on the 370Z. If you're about to fling a car into a corner, it behooves you to not upset the balance by shifting carelessly. Again, AIUI. I don't track anything.
Double-clutching reduces the speed difference between the shafts that the synchros have to absorb, thereby reducing wear. It also lets you shift faster on track, or at all in a car with cranky synchros.
The '86 BRAT I used to own was very leisurely about the 3-2 downshift without double clutching, and downright lethargic from 2-1. If you wanted to be ready to pull away from a stop sign promptly, double clutching it into 1st as you rolled to a stop was necessary.
I can see shifting without the clutch adding wear to the synchros, but I've definitely had to do that too when the clutch went out on the '76 TR6 I used to own. Which admittedly had a very forgiving transmission, thank goodness.
Meanwhile, I haven't put enough miles in our '47 CJ-2A to master a smooth 2-1 downshift without grinding the gears, even with double clutching. That promises to take some practice. Practice that'll have to wait until the steering is sorted well enough to get it inspected, plated, and get it up to 3rd on a paved road. 2nd gets it moving quite quickly enough, thank you very much.
Rereading this before posting makes it sound like I've owned only terrible cars. I assert that they have character, and that's what matters. And only the BRAT was a daily driver. Apart from it, my daily drivers have all been pretty reliable and sensible cars.