Why is a penetration test considered to be more thorough than vulnerability scan?

Vulnerability scans only do host discovery and port scanning by default.

A penetration test actively exploits vulnerabilities in the targeted infrastructure, while a vulnerability scan does not typically involve active exploitation.

It is not – a penetration test is often performed by an automated tool, while a vulnerability scan requires active engagement.

The tools used by penetration testers tend to have much more comprehensive vulnerability databases.