It's because upgrades on that route are nearly impossible for anyone, especially on a Friday. It's not possible to know how many GS are taking the flight (except by watching during pre-boarding -- but, even then, not all GS members choose to pre-board). However, if you purchase in advance, business class is typically $300 more than coach. Paid tickets end up being very popular, which is why upgrades are quite rare.

But, yes, on a G fare, you'd be behind every other 1K on the plane for an upgrade, plus all GS'es. And there's a good cache that every single one of those passengers used an instrument, as there really aren't a lot of better flights to use them on (when they clear). I wouldn't be surprised if your position on the waitlist at checkin is no better than number 10.