This is just our preference. We don't have anything against ad-supported or IAP-supported games. We just feel that there is still a pool of mobile players out there who don't mind purchasing a casual game outright.
And who knows, we might decide to collaborate with a publisher on a future game. We'll see what the future brings.
I can only say anecdotally from my own experience, but the games we had listed for a price got 1% or less of the downloads of the same game after we made it free. People complain about free with IAP, but the $ shows otherwise.
If you want to do this as a business, free with IAP is a must.
Out of curiosity, when were you approached by publishers? After you had launched?
Just my 2 cents.
This is especially the case in multiplayer games. Making it free removes a check on "low quality users" - e.g., hackers, griefers, etc.