Why are the Eagles 7.5-point favorites?

Our weekly Q&A with Dave Staley of sportsbook.com:

Q: What's the line for Eagles-49ers on Sunday?

A: The Eagles are currently 7.5-point favorites as they host a 49ers team that still has an outside shot at making the postseason. The opening number was minus-9, and then moved to minus-8 on Wednesday. Even though 69 percent of the bettors are on the Eagles, this line keeps shrinking. I think this number will go back up and can't see it going to 7, so if you are on Philly, don't wait too long.
 
With the Eagles' impressive win last week, they control their own destiny in the NFC East. So much so that bettors piled in on the NFC East odds this week, and Philly is now listed as the -600 favorite, compared to plus +140 just last week. While there is little to no value in that number, I believe the Eagles to win the NFC at +700 is intriguing. Winning the conference and Super Bowl is about peaking at the end of the season, rather than being the best team during the regular season.
 
The key for the Eagles cover will be containing running back Frank Gore, who rushed for 167 yards and a TD against the Cardinals. If the Eagles can keep Gore somewhat under wraps, I don't see any way the Niners can cover the number.
 
Quarterback Alex Smith has thrown nine interceptions in eight games, which isn't good news for San Fran backers as the Eagles have 20 picks on the season.
 
Additionally, Philly ranks fourth in the NFL with 36 sacks, while the 49ers rank near the bottom of the league (23rd) in sacks allowed with 33.

Q: What about the over/under?
 
A: The total currently sits at 42.5 after opening at 43.5. This one seems just about right to me, although I'd lean over if I were betting it. I can't see the 49ers putting many points on the board so I think it comes down to how many points the Eagles put up against the stingy San Francisco defense. Although their average points allowed number is relatively low, a number of teams lit up the scoreboard against them this season.
 
Of the eight offenses they faced that currently rank in the top half of the NFL is scoring, five of those teams scored at least 24 points against the 49ers. Of course, like any potential total wager this time of year, it's important to monitor the weather closely.
 
The over is 8-1-1 in the Eagles' last 10 home games.