That's exactly how Civ 5 got me into Steam--I really cannot resist the latest Civ, which is also what causes me to upgrade my computers. I am seriously addicted. At least Civ 5, unlike the new Sim City until recently, did not require me to be on-line to play. I can't say I've come to love Steam--tolerate would be more accurate. The Civ 5 workshop is way better than the Banished workshop, which I do not use. The fora on Steam are mostly mindless drivel.
Civ V is actually the only game I use the Workshop with. Every other game I mod, I use either Nexus or other sites. I am not a fan of the Workshop at all. Even when it's working properly, it's subject to some modders doing silly things and breaking your save with a bad update or other problem. Plus, and I am probably being judgmental here, I see a weird sort of entitlement springing up around Workshop, as though modders "owe" users Workshop versions of mods, and game devs "owe" them Workshop integration. Makes me sad, and makes me feel old, because I really want to say, "I used to have to switch floppies 16 times just to play the Wolfenstein demo. Shut up. And get off my lawn."
I don't mind Steam. Especially compared to, say, Uplay. I used to hate Origin but it's improved a lot since I started using it (Mass Effect series got me using it to begin with), and they have the "on the house" games now, and I'm a fan of free games.
Uplay, however, is irredeemable in my mind.
I definitely understand why a lot of people prefer to buy discs and be done with it. I, however, had to replace Civ III, AoE and RoN more than once (more than twice, actually) due to disc failures, lost discs, etc. I'm not good with discs. At all. Steam is great for me in that respect.