This is one of the major issues with these languages that were initially designed by amateurs (I mean that in the positive sense, someone who does something because they care about it, and not because they are paid to do it). Often they simply did not see the long-term benefit of adhering to the limits of a "standard" architecture (i.e., context-free, unambiguous grammar, decidable static analysis (lookup!), multi-pass implementation). Yet these hackers still made a successful product. Now others must live with the consequences (for another example, have a look at javascript's scoping - I strongly suspect that it was a beginner's mistake that made it into production).

That particular syntactic ambiguity in C++ would have been trivial to fix (and could still be fixed today!), but no one really cares (and it would not be backwards compatible...).

Another example is the current situation with modules in C++. Instead of looking into the diverse ML implementations or even Java and trying to get the system right, the current discussion goes into wild compiler hacks just to avoid a simple limitation on filenames.