I'd think that companies use commercial grade internet, and normal people use residential internet. If so, then it would be easy to imagine that the ISP blocks some features for the residential subscriptions.
Many businesses don't bother even subscribing to a business package, because something like a static IP is unnecessary for them.
Further, the point regarding VPNs still stands -- think of the chaos it would cause for many people working from home (on residential connections). And that's just one example.
I don't find it plausible for an ISP to block this.