I never washed my parts when I built AFV models exclusively, but with the extensive masking required for aircraft models, I do it for them. I haven't had any problems with masking tape pulling up the paint on any of my previous builds but I neglected to wash the wings of my current S.E.5a project and I attribute that to my paint peeling issues when executing the rib shading. I can't come up with any other explanation.
I just use dish detergent and warm water too.
Cheers,
Chris