Some episodes missing from the DVD's?

Hey all,

Having just found this group this morning and spending a LOT of time
at www.gotfuturama.com, I was quite surprised to discover the
following:

"A Leela Of Her Own" - some baseball episode not on the DVD's?  What's
the story here?  How many other episodes were not put on DVD?  Even if
they're not great, I'd still like to see them!

There are 4 box sets for 4 seasons on DVD, yet www.gotfuturama.com
lists 5 seasons.  What happened here?

Also, I've been watching all the episodes with commentary.  Why is
Katey Sagal NEVER mentioned and makes no appearance on any of the
commentaries?  Was it just a scheduling problem?  I'm assuming it's
some mundane explanation since she will return for the new season next
year.  YAY for the new season!

Dave S.