It's genuinely been a good deal on paper for a few decades - it's far cheaper than keeping your own equivalent military, which would've been prohibited by the Japanese constitution anyway before recent reforms. But the US has obviously proven to be an unreliable and dubious partner in recent years, and the very public and high-profile issues between personnel and locals is well-documented and has lasted decades.

Furthermore, the US is painfully aware of Japan's economic crisis, and that it is barely managing to keep the yen from crashing while also preventing an interest rate hike that would bankrupt it on loan repayments. This is US abuse of an ally to try to have their cake and eat it too.