There are quite a few videos on YouTube showing people simply changing the color of their cars. It doesn't have to be the full racing livery. I don't know that I'd ever do it either, but it's certainly a curiosity.
I'm a bit less introverted. I want my weekend fun car to be FUN. I drove a Lotus Exige on the street and would love to someday buy a Caterham. I would be fine with a few Martini Racing decals ... although I think it wouldn't look good on anything but white, silver, or black (so a full body wrap would be required). There are some guys who have wrapped their E30 M3 street cars to make replicas of the Jaegermeister (orange) and Warsteiner (white) DTM cars. They're just fun. Being able to do it without making any permanent marks on the car is even more attractive. Get sick of it and just remove it.
I know that Porsche actually sold a Martini edition 924 many moons ago. Martini Racing decals for the 924 are still actually available for purchase. Lancia had a similar special edition Delta Integrale with Martini Racing livery. They actually sell at a huge premium if you can even find one for sale. I don't think it's that totally over-the-top. Especially for a sports car that is just a weekend toy. Ferrari's Challange Stradale cars have stickers ... as do 911 GT3s, etc.