Steam can be used for free without having to provide a credit card or bank account. There are free games on Steam that only require a free Steam account.
The most popular free games are:
- Counter-Strike (CS:GO) is a real-time strategy shooter that has been developed and improved by Valve for over 10 years.
- Dota 2 is a multiplayer online battle arena developed by Valve and is the successor to the popular Defense of the Ancients modification for Warcraft 3.
- Path of Exile is a game with similar gameplay to Blizzard's Diablo series.
These free games alone have brought Steam millions of active players, and Steam knows it, which is why you can install Steam for free on the various platforms: Windows, Linux, and macOS.
Of course, Valve, the company behind Steam, came up with something when it decided to make valuable games free: players can buy in-game items.
The trend for years has been to make a base game cheap or free, and in return, motivate players to buy additional content and other benefits for the game in question.
Valve has always been concerned with making long-term profits, not quick ones. You can see this in Valve's free-to-play games, which make big money in the long run, not in short periods of time. So it's safe to assume that Steam will continue to be free in the future.
You can find the installer for Windows, Linux, and macOS here. On Linux, you can also install Steam via the operating system's package manager.