Well you're definitely entitled to your own opinion. It doesn't change the sound at all though you're right. I just think it looks cleaner overall, seeing more pipes in the flesh gives it a more muscular look IMO.
Just out of curiosity, what are you doing constantly that you're jacking the rear up all the time? I can understand people like RichV that track their cars and need to change out tires and make adjustments on the fly. But the only times that I've ever been under my car for the years of my ownership have been to install my lowering springs, change my trans fluid, do an oil change, change the front ball joints, and to change the wheels. And two of those things didn't even require jacking the rear of the car.
It may add a more aggressive look but it doesn't do nearly as much for the car as a lowered stance and wide rear wheels and tires. If that's all you've done with your Mustang then I can totally understand why you'd be for this as really it's next to nothing as far as mods go. Honestly if i had to jack my car up once or twice a year even then I wouldn't want to have to deal with these stupid exhaust pipes under the axle. I HATE messing with the exhaust, it's annoying as hell trying to get everything to fit right, be even, etc. but just because I don't track my car all the time doesn't mean it's always on the ground.
I've pulled the engine, pulled the trans 3 times, had 4 different catbacks on it, several midpipes and headers, I've done the suspension 3 times including K member install, brakes, changed the wheels a couple times, I mean the list goes on. You don't only have to raise your car up if it's a track vehicle, you just need to get more into the hobby then you have so far.
That being said I guess you could put the jack stands under the rear axle to keep it from hanging while working on the car, but that's going to limit what you can work on at the rear of the car.