I'd assume people who don't understand the crucial difference between the freedoms you want in a library, and in a binary, so just cargo-cult imitate the library-centric default found in the Rust package ecosystem.

Imagine you get an appliance running Linux, but the vendor has made an unknown number of closed-source edits to core system tools. Perhaps cp now has built-in DRM that limits what files may be copied, automatically stripping all but the lowest-resolution stream from digitally-signed video files. Perfectly legal under MIT; GPL'd force them to release the modified source and build instructions so you can strip unwanted functionality. And while a GPL'd library might infect the rest of any application linking to it, a GPL'd binary doesn't further constrain others, there's a natural boundary to the main complaint people have about the license, one which fits perfectly with system tool use-cases.

I can only see people who give up the freedoms that protect them, to gain freedoms that mean nothing in an end-binary, as fools. Best case, too lazy to care.