Zuckerberg doesn't seem like a potential candidate for the JRE podcast because of his secrecy and self-preservation when it comes to interviews and, in general, confronting the public audience. Sure, he's had some moments where he "interacts" with people who ask him questions, but most of it is smoke and mirrors alongside heavy planning/verified questions beforehand.
Is that bad? No. To each their own. However, Jack Dorsey and Elon Musk are somewhat the opposite in regards to how they communicate with the world of technology/gen. pop. Both are somewhat upfront and answer questions to random people through Twitter and many other social media services, while Zuckerberg prefers to "do his own thing". Joe Rogan is not the type of podcast host that would allow pre-screened questions or any type of censorship. He has that mentality of "I have nothing to lose", which is rare in today's publicity-focused world.
I'd love to see Zuckerberg on there for pure curiosity and to see what would happen when Joe hit him with some tough questions, but I totally agree that it's probably not too likely unfortunately. Jack Dorsey at least wants to make the effort to appear caring about the worries of his users, the same can't really be said for FB.