Here in the UK it would be impossible to live without a letterbox! Government departments will not send mail to a PO box, same for ebay, amazon and all other online sellers I've dealt with. The only other option with online sellers is parcel shops or pickup points, non of which are ever convenient for me. And if like me you are a knife collector, UK sellers will not send to any other address but your registered address.
Also, PO boxes aren't cheap here. You can redirect mail for limited times, and mail can be held for time away on holiday, also limited.
The downside to a letterbox is junk mail! So I've started to return junk mail, with a twist! I send one junk offenders mail to another in their post paid envelopes! Just a bit of their own medicine.