Why? Interested in your reasons. One plausible one is that trusting an author you know can be more practical than examining every line of a massive open source code base. Could that be a reason? Others?
A more precise way to state my preferences:
I trust _crypto_ from Microsoft, Apple, or (especially) Google more than I trust _crypto_ from a developer I've never heard of before. I do not as a rule trust rando closed-source projects.