In California you cannot make an employment contract lasting longer than seven years. So at the end of the seventh season they would have had to renegotiate the entire cast and crew's contracts which would have been pricey.
That's what happens when you comment right before going to bed...
I want clarifying as most as I was making fun of the LLM in the picture, which did put "an eighth season would've been too expensive" as a reason for the almost-cancellation after season three. That might've been a reason to cancel in the end but not then.
That’s the opposite of what I heard while TNG was in the air.
Paramount renewed TNG in three-season blocks. They greenlit three seasons and renewed for three more, then chose to add an additional season knowing it would be the last. They repeated this tactic with both DS9 and Voyager.
At least that’s what I kept hearing during the 1990s.