Because of the Maine voters.
No, why Really?
Indeed, and typically it's voters who are fearful of straying from the government teat.
Maine is one of the eight states that spends the most on welfare per capita.
https://www.foxbusiness.com/features/states-that-spend-the-most-on-welfare
(NY, Alaska, Mass, Vermont, Minn, Delaware, NM, Maine)
Because of President Wilson and the progressives that passed the 17th amendment. When this passed, the states lost their voice control of the federal government.