Well there's an option in Steam to backup your local gamefiles to CDs or DVDs.
Hmm, I was not aware of that one. Another great steam feature
Seriously though, as a HOI3 MPer, I am very much glad that HOI4 will be on steam. I intend to eventually play it on MP, and HOI3 without steam support constantly fails---the metasever was unreliable, and connection by IP even with a good connection is proon of out of sync issues as well as random crashes.
Steam can provide alot of stability with this.
I am loathe to trust in a third party to let me play my games, but so far, Steam has really delivered for me. I can't fault them, their business model is fair and strong, and they provide great value to developers and customers both. They're great IMO.
If they stopped being so, I would not buy my games from them.