Of course I'm generalizing, and a lot of C# programmers write great and reliable code. The point is that they often don't -need- to write great code, because lousy code is good enough for all business purposes (except when the software is your product, which is rarely the case).
The second issue is that people who choose C for their projects tend to (a) understand low-level concepts, (b) care about speed / memory usage / reliability / dependencies, (c) don't consider development time that important. That you create more reliable software that way is obvious - the same programmers would create reliable software in C# (or similar language). But there aren't many situations in which development speed doesn't matter, speed and memory usage don't matter, dependencies don't matter but, for some reason, reliability is very important.