If every kind of food is more or less equivalent, what reason do you have for choosing one meal over another?
Personal taste, culture, past experience, what “feels” right.
I know several polytheists who engage in multiple religions actually. For example: there are aspects of Asatru that appeal to them, they have an affinity for Hekate, they have a small shrine to Cernunnos because of a Gaulish ancestor, and Odin told them they should learn something about American hoodoo. And they’ll occasionally go to Catholic Mass in Latin to soak in that atmosphere. A lot of people believe that God(s) is God(s), and the mythology is more or less interchangeable – and the same people have no beef with science.
There is a lot of cross-pollination between pagan and reconstructionist groups. They go to the same bookstores and conventions and share stories and experiences and advice.
Okay, let’s set aside the religions that use fear tactics, for the supremely logical reason that I think they suck.
So that leaves “there is some personal benefit.” You can say that about every human activity – there is always a motive. I get personal benefit out of playing videogames and reading science fiction, too. The thing with personal benefit is it’s not necessarily exclusive.
The attitude I see from polytheistic religions is “this religion is not for everyone. If it suits you, great. If it doesn’t, we are all better off if you do something else.” There is no sales pitch, no “we have the secrets of the universe and those other guys don’t!” It’s more like “this is one possible path to spiritual growth.” I’ve never seen proselytizing, just people sharing their own enthusiasm and being pleased if someone else picks up on it too.
The closest I’ve seen to exclusivity is an (optional, voluntary) oath to serve particular gods first, at a certain advanced level of commitment, for people who have already been involved and active with that religion for some number of years.
(As far as how I am familiar with this stuff: I have been pagan of one flavor or another since high school. I was Kemetic Orthodox (ancient Egyptian reconstructionism) for 15 years, and a priest for most of that. I have looked into Wicca (and found it not personally tasteful due to gender essentialism), Feri, Celtic paganism, Chaos Magic, Discordianism (fnord), Shinto, Taoism, shamanism in general, the intentional worship of fictional deities, and most recently Gnosticism. Right now, I consider myself floating, but influenced by several of those traditions.)
(Oh, and creationist claims that their story is wrong and evolution is right? Ludicrous. But then I think anyone who takes religion as an explanation for the physical universe, instead of a deeply personal art form, is doing religion wrong.)