Overcall this river?

[madscratch]

http://twodimes.net/h/?z=1335855
pokenum -h 8h 8d - ad 7d - 6c 8c - 8s 9s - kd 4c -- 3d 5h 7s
Holdem Hi: 741 enumerated boards containing 7s 3d 5h

cards win %win lose %lose tie %tie EV
8d 8h 192 25.91 541 73.01 8 1.08 0.263

Ad 7d 145 19.57 596 80.43 0 0.00 0.196

8c 6c 176 23.75 557 75.17 8 1.08 0.241

9s 8s 146 19.70 587 79.22 8 1.08 0.201

4c Kd 74 9.99 667 90.01 0 0.00 0.100

Ok, so in this scenario pretty much everyone's getting the odds to call. And we're only slightly ahead. I would have thought we'd be a bigger favorite. Is this why we just call?