I think you have to prove yourself indispensable and really charm people with functionality that is surprisingly effective. I pay for iCloud (former) and Spotify (latter - their discovery constantly astounds me).

I need something like Dropbox and begrudgingly use the free tier interacting with my clients who use it, but I find myself trying to avoid paying for it or locking in on it. Something about it is just off-putting.

Sure they do, they just need more. Plenty of people are paying for iCloud and Google.

Dropbox' strength is sync and sharing, but they kneecap that by double-counting sharing capacity. I can't share a video with my wife (a non-subscriber) without paying again)