Why wouldn't they dilute their brand? They've built up a reputation of building a high end product. If someone begins selling a product that looks nearly identical to their own, that's of inferior quality, how does that not affect their own reputation?
Because professional engineers choose test equipment based on functionality, and color schemes fall pretty low on the list. (yeah, this may be hard to believe if you have a primarily software background)
Sparkfun isn't a site for professional engineers, it's a site for hobbiests. Professional engineers typically don't buy shoddy gear which can end up blowing their arm off.
Professional engineers aren't the only people buying multimeters. Lots of people who work as electricians and wiring techs also buy multimeters, and many of them do buy by brand which is, conveniently, color scheme.
