Why Legislatures in Different States Pass The Same Bills

Because conservative legislators bring back copies of the same bills from the ALEC conferences  they attend  corporations pay for them to go to (via Ritholtz):

Corporations pay hefty fees for the opportunity to discuss policy with legislators at ALEC's conferences, and they also host banquets, open-bar parties and baseball games. Legislators, on the other hand, pay a nominal membership fee, and can be eligible for "scholarships" that pay for their conference attendance. When the legislators bring the model bills back to their state capitals, the role played by ALEC—or by the corporations—seems to be rarely, if ever, disclosed.
Crucially, ALEC says it is not a lobbying organization, and thus because of its nonprofit status, it does not have to disclose its donors or the amount of their donations. (The Times says Common Cause is trying to challenge ALEC's nonprofit status.)

This is a perfect fit for the lockstep conservative movement.  One state passes an idiotic bill, then 6 or 8 other states are passing the exact same thing.  It is kind of creepy that they write bills for immigration reform, destroying public sector unions and even ridiculous photo ID requirements for voting.  The corruption of the democratic system is stupefying.