While I had been aware of tarot being used for games (I had long had a French suited pack but lacked the French to read the instructions), I discovered the games while studying philosophy via Michael Dummett's work. It wasn't something that I expected to see on his list of publications and so I obtained a copy of The Game of Tarot and never looked back. I can't tell you how many hours were spent in my third year playing various games! I suppose, though Dummett was not atheist by any means, you do find more atheists and agnostics in philosophy than theists.
It is a funny thing but I do find antheists and agnostics are more likely to be willing to try the games than others who, in my experience, find it harder to overcome the perception of the cards as occult. Such people will either see them as something they shouldn't mess with or as something it would be wrong or disrepectful to play a game with.
I remember a couple of years ago being on a train with my niece and brother in law. We were playing a game of tarot with a French suited pack, which they found easier to use. As the train became crowded, a man asked to sit with us and my brother in law asked if he would like to join our game. He looked disturbed when the name tarot was mentioned and even after I explained that this was a simple game pack, with none of the images associated with the occult, he still got up and said "...I don't mess with tarot cards, I'll find somewhere else to sit."
This kind of response is not uncommon to me but it is hard to draw any reliable conclusions from the sample of my own experience.
I would venture that an atheist or agnostic is less likely to believe in the supernatural or occult and would therefore not be troubled by any such preconceptions.
Closrapexa, I don't think that secular is what is meant. Secularism is the belief that religion and state should be kept apart, and while many secularists are atheist, many are also religious - even devoutly. Atheism means belief that there is no God, although many in recent years seem keen to use it to mean lack of belief in God. Certainly, closed mindedness is not unique to religion but I do think that religions can be particularly prone to it, as faith allows them to trump any reason, while the closed minded faithless lack even that as an excuse.
I would say that I'm not completely comfortable with the disctinction between the religious and the free thinking. There can be different arguments for not making that distinction, one being that religions are not always held as objective beliefs but sometimes as subjective ones - that is, neither true nor false but rather expressions of how a person experiences the world and brings meaning and value to it.