A case like this can be sold to developers in odd ways. Devs typically think that people who download things have way more insite than they do and can assess what putting the certificate on the device means. The team that started the project likely feels that this helps them build a better experience for their users.

Facebook in general seems to have good intentions and terrible awareness of what is crossing a line. They really wanted their platform to be the center of everyone’s lives and now appear completely unprepared for the consequences of pushing that agenda so hard.