Honestly, after downsizing from a three-bedroom apartment to a tiny house on wheels, I found it was both. My utility bills dropped to almost nothing, and I paid off my student loans faster because the mortgage was so low. But then there's the lifestyle shift. You have to get creative with storage, like using vertical space for books and a fold-down desk for work. At first, it felt restrictive, but now I can't imagine accumulating so much stuff again. So for me, it started as a money thing and morphed into preferring the simplicity.
Read an article that called minimalism a gateway drug. Once you cut the stuff, you start wanting less everywhere else too. Makes sense from your bills to the fold-down desk.