I use Google Drive, but I can see the appeal of Dropbox for someone who doesn't need Drive's web UI features and extras and just want something that works.
Now, with Team Drives and File Stream Goolge is catching up and of course Google Docs have no equivalent in Dropbox. (Dropbox paper is very limited). But Team Drives have very weird limits (max 20 subfolders deep, max 250000 files)
I've stuck with Dropbox for a while because it's easy to set up, portable, the iOS app is fantastic, and I feel like my data isn't being siphoned off to advertisers.
The other thing I've noticed is how fickle Google is with their products, either not advancing them or straight up killing them. I used to use Listen for Podcasts and Reader for RSS and got disheartened when those were killed off. Dropbox is my latest switch, hell I even use DuckDuckGo more these days, too. The only Google products I can see myself using long term are Gmail (with my Google Apps Domain account) and Photos. Also, Maps is still the best Maps software. Other than that I don't use their services much at all these days.