Per the trade papers:
... With its budget at a reported $150 million, Mars seemed to have the deck stacked against it almost from the start. The pic, from Zemeckis' ImageMovers, was an orphaned project, grandfathered into the Disney pipeline as the Dick Cook regime ended. ...
A summary of Imagemovers' MoCap box office:
Mars Needs Moms -- $15.9 million (world cume) -- cost -- $150 million
A Christmas Carol -- $321.5 million -- cost - $180 million
Beowulf -- $195.3 million -- cost - $150 million
Monster House -- $140.2 million -- cost - $90 million
The Polar Express -- $270.8 million -- cost $170 million
Although Christmas Carol and Polar Express picked up considerable coin, the movies' production costs were high. The Mouse (and before it Sony and Warner Bros.) were probably looking for higher profit margins. Or in some cases, just plain profits.