What are your most-played games on Steam, and why have you spent so many hours on them?

Team Fortress Spy being shocked.

THE PCG Q&A

Find all previous editions of the PCG Q&A here. Some highlights:
- What's a weird quirk your PC has?
- What should boomer shooters be called?
- Have you learned a real-world skill from a game?

You can sort your Steam library in various ways. Via release date, or size on disk, or percentage of completed achievements. One option seems to exist just to give you an existential crisis: Sort By Hours Played.