Why is it always front disc brakes that need fettling?

So I changed my wheels today to some hope gravel wheels and they are very nice

However, why is it always the front disc caliper that needs adjustment when you change your wheel set? I would have thought that the rear with all of the other drive and other gubbins would require a lot more adjustment. In a couple of bikes where I've changed the wheels, it's always the front wheel that gives me the most problems.

We are currently on alignment session number 3 in the last 4 hours trying to get rid of either brake rub or the pads rubbing slightly on the brakes and reaching harmonic resonance with the rims....... Seriously, I've never managed to almost go deaf due to brake rub but today I think I might have managed it. What's weird? Is that in the maintenance stand? The wheel spins freely without any rub but as soon as I get out and about 3 to 4 km into the ride you start to hear a distinct squeal and I have to touch the brakes just to stop the squeal. Riding with the brake lever slightly depressed stops the squeal completely.

Hopefully the last adjustment session will be the last and this next soak test ride will be successful. Otherwise my 120 km ride tomorrow morning will be a very loud one!

Any suggestions as to how to quieten down the brakes would be greatly received.. so far I have:

Cleaned the discs

Cleaned the pads

Manually realigned the caliper

Manually realigned the caliper again

Changed the pads around

I'm running out of options? I know on cars people put copper slip on the back of the pads? I've never seen this done on a bike but is this a thing that people do??.