In the EU, Apple posts prices including VAT, just as local regulations require. That's because the EU has this enormous influence over the American company Apple.

Or is it because companies generally tend to follow the law of wherever they operate?

It's not unjust or morally wrong to post prices including VAT, so I have no complaint about Apple doing that. When a foreign country's laws require companies to do things that are unjust or morally wrong, I want companies to choose not to operate there rather than follow them. Similarly, I'd want companies to pull out of Australia rather than backdoor their encryption.