Because if the Rams get to 4-1 there's a - iirc - 77% chance of them making the playoffs. They're at home with a full, loud house.
And, more than that, it'll show if progress has genuinely been made. We know Fisher's Rams can beat the Seahawks, the Cards and the Bucs. They've done it before. It's games like Buffalo at home where Fisher's teams have laid an egg.
Good in the division, lousy outside it...
The next division game is week 15. There's a big stretch of these 'lousy outside it' games to come.
Sunday could signify actual progress. Or not.