Because all homogolation specials should be available without a roof
A collection of photos of the 1/18 scale CLK GTR Roadster from GT Spirit
The only way Mercedes-Benz could have made the CLK-GTR more insane was to cut the roof off it, so they did. Six CLK-GTR Roadsters in total were made; the first of which being a prototype built out of a spare race car. One headed to Brunei and another one become a very notorious and expensive lemon in the US. Thankfully mine only cost me under $100 and wasn't too hard to find.
This is a 1/18 scale resin model of the topless V12-powered beast. Yes, it is an entirely closed model, meaning you can't remove that giant rear hatch to see the engine or play with the butterfly doors. What you do get, of course, is an incredible paint job, tight seams, headlamps as smooth as glass, and a tiny tow hook up front. Surprisingly, the model Roadster version of the car is relatively easily available, with second-hand deals on eBay popping up all the time. The iconic closed roof car is a different story.