Teams can adjust their park to fit the team, as Cleveland tried to do with Alex Cole in the 80's, or they can adjust their team to the ballpark, as Dan O'Dowd with Colorado is trying to do now. Familiarity with the nooks and crannies of the park affect defense. For example, tall fences, large foul territory, ivy walls, outfield corners, etc. Teams can be built around the particulars of a park, unlike football and basketball where field dimensions are dictated by rules. Players are more comfortable staying at home with families.
Players get tired toward the end of a long roadtrip.
Other sports do not have as lengthy road trips. I was going to write about how teams with great April records fare over the course of a season, but a couple of other writers have already written articles on the topic. Used under License.