This should be far more secure and privacy friendly than a Sim card of a cellular connection. Why isn't this done more often? What are the Pros and Cons. I bet the price is similar as well.
Why not is the question and that comes down to guessing. Sheep do what they are told so don't need to guess much there. Those who are not sheep have to go through a long journey to gradually keep increasing their privacy and unlearn the sheep habits we've been conditioned to have.
The end goal is to throw away your phone because you can do everything on your computer instead including buying a phone number, using voip and take and make calls. Phones are unnecessary spy devices used by sheep.
privacy is about making effort to protect it. With your logic you should just use google chrome browser and be signed in to google because it makes an easier experience. Then install alexa in your home and make it a smart home, it also makes life easier.