>> We must wait for relevant news from the principal programmers; whoever hears any should please inform us.

Most of them post with some regularity at the abcusers group on Yahoo.

>> The reasons why they didn't bother so far still escape me

Because creating a fully featured specification that is backwards compatible is incredibly difficult, and different programs cater to different users with different needs.

For example, how do you write ABC for scordatura tunings that will print and play correctly?