Can anyone tell me why when you have 2 tracks mixed after you mix one and switch to either deck you cant just change the BPM?

I seem to have to move the pitch fader up or down until it levels out to the original BPM and then i can change it

While doing this often the BPM range changes to WIDE as well which is even more annoying as I have to then manually change this with the mouse?

Please help this is driving me insane.

TIA Bart