Cool. Sometimes nonprofits like churches do the same in the US. Small businesses tend to use their home address (for tax reasons) or the address of a membership-based office space vendor like Regus (pre-coworking and pre-WeWork).
In the US, it's possible for anyone to receive a few pieces of mail or packages at a post office without a permanent physical address using general delivery.[0] For people without means who receive significant mail, the local USPS postmaster can grant them a PO Box.[1] As of 2018, there were 1.3 million no-fee PO Boxes out of 21.3 million.[2] (I assume this is for very low income people and actual homeless people and combined with some tens of thousands of deceased homeless people and perhaps as many cheaters of means taking advantage of the system.) And to workaround the artificial discrimination against PO Boxes for all users, USPS offers Post Office Box Street Addresses (PBSA).[3]
No-fee PO Boxes also cover situations in which USPS doesn't deliver to a house in a rural area (no carrier service, as noted in your source [2]). It's very common in many small towns.
In the US, it's possible for anyone to receive a few pieces of mail or packages at a post office without a permanent physical address using general delivery.[0] For people without means who receive significant mail, the local USPS postmaster can grant them a PO Box.[1] As of 2018, there were 1.3 million no-fee PO Boxes out of 21.3 million.[2] (I assume this is for very low income people and actual homeless people and combined with some tens of thousands of deceased homeless people and perhaps as many cheaters of means taking advantage of the system.) And to workaround the artificial discrimination against PO Boxes for all users, USPS offers Post Office Box Street Addresses (PBSA).[3]
0. https://faq.usps.com/s/article/What-is-General-Delivery
1. https://faq.usps.com/s/article/Is-there-mail-service-for-the...
2. https://www.uspsoig.gov/reports/audit-reports/no-fee-post-of...
3. https://postalpro.usps.com/PBSA