Foundation dropped IE8 and below supports at very early stage. I think it caused them losing the Community.
Vendors like Zurb (or in-house team for their own company site) usually working on large projects and able to make every decision clearly and fixing any problem they facing. However, for most of developers, they can't afford the cost of it. While there's Boostrap exists, why do you put yourself into risky?
A lot of backend developers using Boostrap. They even don't understand basic CSS.