I just wonder if there's rationality behind not changing this (by either switching to a different language, fixing it or, hardcore mode, create a new one).

I know from a very, very different field that you often have to deal with decade(s) old technology because your employee/professor/etc is just used to it and, 15 years ago, it simply was the best option. I guess it's an equation that puts time spent learning its quirks vs time saved using a more sensible tool. While tiresome, "learning" might actually be the faster way to get things done. But it also carries so much ballast that, if there's a better alternative, must waste millions of frust-hours (and actual errors), especially for newcomers who could just as well learn a new tool - faster.