MLB question

Maybe I just haven't been following baseball much lately, and there is an obvious answer to this question, but:

Why not move the Houston Astros from the NL Central to the AL West?

Three advantages: One, it would even up all of the divisions at five teams; two, Astros-Rangers could be a great divisional rivalry; and, three, it would shorten the travel distances for in-division games for the remaining NL Central teams.

Plus, it's not as if the Astros have an age-old rivalry with anyone else in the NL Central…gosh, do the Astros have a serious rivalry with anyone? (Well, the Mets, but that's purely one-way.)