another silly phonology question

I've been trying to look at phonologies and how symmetry tends to operate
in them.  I'm probably noticing out of a weird sample, but there seem to
be a number of languages that just have /h/ as a glottal.  Is there a
reason for this?  I was almost going to delete /h/ from Chevraqis because
I didn't like just having *one* glottal, but looked at some actual
languages and got confused.  Are there certain tendencies for *how*
language phonologies violate symmetry, when they do?

YHL

P.S.  After missing bunches of messages I now realize that OT probably
means optimality theory.  I kept thinking, "It can't be 'Old Testament,'
but what *could* it be?"  <Wry g>  Thanks to Roger (was it you?) for
posting that website on phonology--I mean to look at it carefully *after*
I get some of my homework out of the way....