Why is the private key in pfx format?

Question

Digital certificates

What is the pfx format for? If authentication takes place in the PKI using a certificate, it contains a public key, the private key is stored on the server, I understand the mechanism of interaction approximately. Then in pfx format, both the certificate and the private key are stored in one file, why?

Answer 1

The PKCS #12 SSL certificate format (PFX certificate) is designed to store and/or transport the private key, the chain of trust from the user's certificate to the root certificate of the certification authority and the certificate revocation list.

Answer 2

In order to transfer both the certificate and the key to the owner of the certificate. As a rule, the container is encrypted, you can't open it just like that. Generally speaking, the use of certificates is much wider than the use of the web, the web is only part, and not the largest.
How, for example, to transfer a certificate with a key to an email user? How to transfer a certificate with a key to a device, some kind of VPN Gateway?