"F-Droid 2.0 now fetches and installs app updates by default."
Why not download source, review, (edit) and compile on the device, e.g., using Termux, Gradle and Android cmdline-tools
Is "convenience" the rationale for the F-Droid app
Maybe it's the same rationale that drives Linux users toward "binary package managers"
Running a malicious build script is just as bad as running a malicious app, so I don´t see why you want that? Also F-droid has fully reproducible builds, so you can be sure you'll get the same binary.
Speed. Most people are going to choose a fast binary download + automated integrity check over compiling from source, regardless of their reason for using F-Droid.