Most companies certainly won't be using "commercial grade internet" in the way that term is usually used. That would usually be reserved for large enterprises, which really only covers a small part of the workforce in practice.

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.