it improves accountability of state level officials between elections, especially where promises have been broken or actions have been strongly opposed
it’s popular. there was a total of 120 measures on ballots in 2020 including 13 in California
it allows voters to have a direct say in framing laws
it allows variation in laws between states that reflect their different political priorities and complexion
it adds as additional check and balance to state executives and legislatures between elections
it increases opportunity for political participation and provides additional support for pressure groups . E.g. 2014 - NRA publicly backed a measure in Alabama
it can cover issues where parties and individual candidates haven’t made a prior promise