Packager middlemen give me a layer of protection against application developers selling out to malware companies.
I trust F-Droid more than $RANDOM_GITHUB_ACCOUNT.
The best of both worlds is where both the developer and a third party certify the builds, as happens with F-Droid's reproducible builds.
On Android you're still left on deciding whose signature to put on the binary, however (I'd prefer one from the third party, differently from what happens with F-Droid reproducible builds).