A quick refresher on the history of the final-week SNF game:
Back in the '08-'09 range, the SNF matchup, which had been set at the beginning of the season, was Jets-Bengals. Jets needed to win to get in, Bengals were locked into their playoff spot (and also knew that if they lost they would play the Jets again in the first round). Cinci rested their starters, the game was a snoozefest, and Jets won to clinch (and then went on to beat them again the following week).
After that, the NFL revamped the Week 17 schedule where all games were divisional, and any game could be flexed to SNF. For the next decade or so, that seemed to work pretty well. There were some good showdowns, even if a couple of the games were situations where both teams had clinched a playoff spot and were playing for the divisional title.
Then a few years ago, there were no straightforward do-or-die matchups in Week 17, so the league just didn't have an SNF game. Maybe that lost them a lot of money or NBC told them it couldn't happen again, but for whatever reason, when there was a similar situation last year they scheduled WFT-Eagles even though Philly was already eliminated, with predictable results: Philly pulled Hurts in a competitive game and handed Washington the NFC East title.
My guess is that this year, they could have forgone the SNF game to avoid even the possibility of a snoozefest, but they gambled that the most likely scenario would be that it's a win-and-in game, and they'll be keeping their fingers crossed until the final whistle of Colts-Jags.