I've done a few of these as fund raisers. When you set a number of X, people know they are doing a good thing and getting, at a minimum, a 1 in 100 chance to win. Gives incentive to buy more tickets.Fair enough. Thanks.
Generally if you sell all the tickets you can, you have to sell them for a buck each and raise about the same amount of money, it takes longer, and getting the tickets/drawing/money to match is a nightmare.