I think dropbox (or any “magic folder” sync) is great as well.
YouNeedABudget used to do this and then “upgraded” to use their own proprietary service that charges $X/month.
I think it’s not just the data monetization, but that frequently data sync is the only feature that requires ongoing services. So if I write software and want to charge a monthly service fee, then data sync is where I can force the service.
Companies can do whatever they like, but jerk companies will make poor designs that require their own magic sync. Smart companies should fall back to a sync folder to allow self-run and just charge me for software.