Is a steamer worth it or rather unnecessary?

To be honest, I'd say it depends on how you cook. If you prepare a lot of vegetables and care about eating healthy, something like that is practical and saves you time - you can cook multiple things at once. Personally I don't use mine very often, but in winter when I come home from ice fishing and want to eat something quick, it's pretty helpful. For most people though, a good set of pots and pans is probably enough, I'd say.