Could be that they're too valuable to pay to leave. Could be that the thought is that enough will want to leave regardless, without incentive. Paying severance generally includes some terms including non-disparagement, so not offering a sep could backfire if there's particularly juicy dirt to dish.

Dell Software Group is made of the many of the recent software acquisitions (Quest, KACE, Boomi, etc.)

The group includes everyone from the software engineering teams to the sales and marketing folks.

I can't speak to why they aren't eligible for the program.