AMC wanted a Mad Men spinoff.
Lionsgate COO Sandra Stern revealed to THR that the cabler wanted Mad Men creator Matthew Weiner to extend the period drama with a Sally or Peggy spinoff series:
When we first started negotiating with AMC, one of the things they wanted was a spinoff. We talked about doing a contemporary one. Given the fact that [Mad Men] ends nearly 50 years ago, most of the characters would be dead. Sally was the one character young enough that you could see her 30 or 40 years later. There was a time we wanted a Peggy spinoff, too, and, a laBetter Call Saul, a minor character going off to L.A. Matt wasn’t comfortable committing to a spinoff.
Ultimately, the failed spinoff discussions led to Mad Men securing a fixed end date, per AMC president Charlie Collie:
We entered into the negotiation and left the negotiation with an aligned goal, which was to get Matthew Weiner to the end of Mad Men.
The seventh and final season of Mad Men returns April 5.