Krzysztof - I think one of the biggest issues over the years with the E21 is CA and other states made post-'75 cars have to pass stringent smog laws. All the original equipment needs to be on the vehicle and it also needs to function. This severely limits any modifications that can be done to the car. Some people cheat and pay off the smog stations which is becoming harder and harder to do (so I hear), others would put the pieces back on every two years when they needed to smog the vehicle, etc.etc.
As you can imagine this is a huge problem and PIA.
As you know, people love modifying BMW's and even the ones that stay stock, the small 1.8L motor (later 79-80), combined with the big bumpers here in the states made them undesirable compared to the older 2002's, coupes, etc. Still very well built and a solid car however.
We used to own one and I love the cockpit, the layout of the interior, and they are cool looking, I love the design. I would love an Alpina version, Hartge, Baur or 323i as well. Those eliminate the large bumpers, smaller motor issues. The 320is with the 5-sp, limited slip diff, Recaro seats, and suspension among other things and limited production still make those desirable; but again, the smog becomes an issue. The thermal reactor was no help by any means.
Bottom line is if I had to pick the main reason why they never became super popular would be the smog issue with such a potential big vintage market in CA for these kinds of cars over the years. If we didn't have snow here in CD'A 6-months out of the year where I live now, I would totally buy a 320is or 323 version as smog is not an issue here. Too bad there was no 320ix or 323ix version made!
Probably would have made for a really cool rally car...
