For online banking (apps), physical addresses and office buildings are also not needed, but at the same time, it also allow you to receive and send money to almost anywhere in the world. Just like bitcoin, online banking requires a smartphone and internet. In fact, if you compare online banking and bitcoin, there are identical in these categories. I don't consider at the moment the other aspects of btc and give analogies from the position of an ordinary person who is not versed in new technologies.

I suspect that these 1.7 billion people don't use banking services and bitcoin for the simple reason that they are either below the poverty line, because of which there are no smartphones and PCs, or there is no Internet connection, or they live far from civilization in small villages. It would be a mistake to assume that every person on the planet will be able to buy, own and use BTC. No. This will interfere with the reasons described above or others.

Don't expect you to get people hooked on the bitcoin. 100% (even a close percentage) of the population of bitcoin can't be covered.