A lot of VC games either have not made money or were barely profitable. First, Nintendo takes a cut (I think around 30%, which is similar to the other download services), then add in the cost of getting it rated (each region requires a separate rating, so you have to pay for ESRB, PEGI, OFLC, CERO, etc.), add in the cost of porting it and testing it and time for employees to do it, and some of the lesser known games would have a hard enough time just making a profit. Adding 3D may actually hurt sales since some people might not be willing to pay extra when they just want the game. Take something like Spelunker for the NES. It goes for $5. Right off the bat the developer only gets about $3.50 from each sale of the game. Assuming the game cost less than $250K, they had to pay $800 to the ESRB for them to rate it. They would need to sell about 229 copies to get back the cost for the ESRB rating, not sure how many to make a profit since I don't know how much it cost to port the game. Developers also want to make as much money as possible, which means spending as little as possible, and they would only add 3D if they think the amount of money generated would be increased.