I can think of a couple of reasons POE isn't used more...
- It's nontrival to learn enough to get started.
A lot of the modules on the CPAN you can pick
up and learn to use in about five minutes.
POE requires a larger investment of time,
due to its inherent complexity.
- Most things can be accomplished without it.
- There is no single feature that is so compelling
for a certain common task that whenever people
have to do a certain thing, they think, "Oh,
for this I should obviously use POE." A lot
of the really popular modules, such as Class::DBI,
are designed to handle a specific type of
problem that people run into often. POE is
more general, which allows people to think, "Well,
someday I'll learn POE, but for what I'm doing
today I don't need it, so I can put it off."
This is related to the previous point.
I'm sure there are other reasons as well.
"In adjectives, with the addition of inflectional endings, a changeable long vowel (Qamets or Tsere) in an open, propretonic syllable will reduce to Vocal Shewa. This type of change occurs when the open, pretonic syllable of the masculine singular adjective becomes propretonic with the addition of inflectional endings."
— Pratico & Van Pelt, BBHG, p68