why do they have DVD options but not streaming for some of these? Is there different liscenses needed for the streaming that they cant get for certain shows? Id love to be able to watch this and other shows again!
The short answer is that yes, there are different licenses.
Thanks to years of precedent from people, libraries, used book stores, and video stores, physical media (like a DVD) can be bought once and sold or rented over and over. This is called the first-sale doctrine.
Streaming media doesn't have any such "first-sale doctrine", so the companies that make the shows/films/books (for example, Disney), and the companies that sell them (for example, Netflix) must have a contract to agree on exactly what shows can be available, how many times it can be viewed, in what forms it can be viewed, and how much it will cost. If Netflix were to stream Will and Grace without getting the permission of whomever owns the rights to it, that would be illegal and they'd get sued out of existence.
That said, it is aggravating and stupid when shows are not available on *any* streaming service (even the pay-per-view ones like iTunes and Amazon).