Well look at the facts. Ever since episode 5 it's had low viewers numbers and show cancelling ratings, but episode 7 is when it bagan having low show cancelling ratings and viewers, and of course the ranking has effect on the ratings and it never had a good ranking.
Rating, Viewers
5. 3.7, 5.51
6. 3.6, 5.22
7. 2.5, 3.54
8. 3.2, 4.89
9. 2.6, 3.84
10. 2.6, 3.85
11. 2.6, 3.95
12. 2.3, 3.46
13. 2.8, 4.17
Usually for a show to stay on television during it's 1st season it has to have about 6.5-7 million viewers with at least about a 6.0 or 5.0 for a it's lowest possible rating, not continuous rating. Carpoolers had niether for most of its run, which shows you ABC had confidence that it would do better otherwise they would have cancelled it and pulled the episodes off the air after the 8th, 9th, slightly possibly the 10th, episode. Cavemen had just about as good of ratings compared with this shows first 6 episodes and it was still cancelled, with top 4 rankings, and with 4.61 being it's lowest ratings but that was from the holidays and the stirke. Hardly anybody watches TV during the holidays so doubling that with the strike makes it so that Cavemen had a very successful final episode for a show that was in it's 1st season.