It could be that your driving habits could be causing this; especially if you do a lot of city driving and/or hard braking.
Squealing can be caused by a number of things; glazed brakes from the above, brake pad vibration due to whatever, brake dust, etc.
Next trip to the car wash you can try doing a little blasting of the brakes as best as possible with the high pressure nozzle. That might clear it up.
No one uses asbestos or has for years and I don't believe it would be matter of not wanting to do it under warranty. I worked for VW for quite a few years and to be honest, I found their warranty labor times and reimbursement to the dealers to be very fair and superior to other car manufacturers.
Hope that helps some.