> I think it was Snowden who made TLS the default.

Snowden's revelations were a convincing argument, but I would place more weight on Google in its "we are become Evil" phase (realistically, ever since they attained escape velocity to megacorphood and search monopoly status), who strove to amass all that juicy user data and not let the ISPs or whoever else have a peek, retaining exclusivity. A competition-thwarting move with nice side benefits, that is. That's not to say that ISPs would've known to use that data effectively, but somebody might, and why not eliminate a potential threat systemically if possible?