I think the reason we don't see a lot about formats is that they're pretty mundane. Not a lot of questions to be asked about them.

The interesting thought that your post gave me was this: formats are no longer worth including in core perl. By that, I mean that if the feature were being considered today, people would say "write a module for that -- it shouldn't be part of the core language." It would very probably be a core module, but not part of the language itself.

I notice that Perl 6 still includes formats. I wonder if that's because nobody ever considered dropping them?
Correction: formatting is done by a module in Perl 6.