Almost certainly liability, when I worked at Napa we were not allowed to work on customer cars, even if it was just putting in a headlight bulb or helping an old lady replace her battery despite the fact that most guys were trained techs. If anything goes wrong just a little, expect a lawsuit.

__________________
TC
Current stable:
- 2004 Mazda RALLYWANKEL
- 2007 Saturn sky redline
- 2004 Explorer...under surgery.

Past: 135i, GTI, 300E, 300SD, 300SD, Stealth