The majority of the population of Utah is accustomed to and accepting of the LDS Church meddling in the details of their personal lives. And the majority of lawmakers are LDS Church members who are in the habit of meddling in their neighbors' daily lives as part of their church duties. Not that they regard it as "meddling", but most outsiders would. The result is a culture where this sort of thing is accepted without much questioning. Historically, the Church has functioned as a quasi-governmental body in Utah, and the legacy of that is all over Utah's laws.
Maybe that is why they were having such a big argument over fluordation of water recently...