It’s not just ideology:

 Another major factor was the legislative resources available to lawmakers: states where legislators had smaller budgets, convened for shorter lengths of time, and spent less time crafting policy were all more likely to enact ALEC model bills (even after accounting for the ideological orientation of state governments). Lots of legislators fit this description: In 17 states, the average state legislator only spends the equivalent of half of a full-time job on legislative work, receives about $16,000 per year in compensation and is assisted by only one staffer. A similar finding emerges when you compare legislators, too: Less-experienced legislators were much more likely to rely on ALEC model bills compared to more experienced lawmakers.