Ghostwriter did get a
spin-off, actually, albeit a few years later and on a commercial channel (CBS).
It's not that PBS "pulled the plug" on shows; it's that being a nonprofit operation, and one led by individual stations rather than the network, made each show more financially volatile. Each show was, and is, funded specifically by corporate sponsors, rather than by a network that in turn makes money from advertising. So if those sponsors pull out, you're sunk - and that's what happened with Where in Time.
This interview with a Brøderbund exec explains the Where in Time cancellation:
As PBS’s audience was further fragmented by new cable channels, and as the production values in their shows required greater costs, the price of sponsorship continued to increase. Eventually sponsors had to pay more for smaller audiences, which was a tough sell in a market where ad inventory was flooding onto the market with new cable channels. We reached a point where we had 2 of the 3 sponsors in place to fund another season with the production values we wanted, but couldn’t secure a third.
He also explains that Where in the World wasn't canceled and then revived, but rather that the creators (i.e., WGBH and WQED) felt the need to freshen up the show:
It was a smart creative decision by the producers to evolve the brand and put something new in front of their audience. We had many meetings to discuss the possibilities after so much success with the original game show, but the producers wanted a new theme that carried over the core values of the original.
It was never about the shows not going well enough. It was about the difficulties that all TV networks were going through in the '90s, changing sponsor attitudes, and the need to keep things from getting stale.
