Currently PowerApps can only be shared within a domain. There have been suggestions about sharing an app outside of a domain, but that still requires a sign-in. I am recommending the ability to share an app publically without any sign-in required for access. It would function like a website.
I can see the potential of using PowerApps to make your own public website. Flows allow you to send emails and get information. You could program buttons to calculate and show what you want it to. These capabilities are not directly possible in a service that makes web-building easy like Square Space. So building it on your own using known Excel-like formulas is an attractive feature.