the ennies mandate isn't to generate sales - although if they do have that side benefit, then i'm sure nobody will complain.
The ennies are to award recognition to those who work in the industry. It's a way for the fans and peers to step up and say "well done! You did a fine job there!" to some people, i'm sure that doesn't matter, but to others it has a value in of itself.
for myself? The ennies have exposed me to things i'd never have looked at before - even from big mainstream publishers. It may be a tiny industry, but there's a lot of product out there every year, and a shortlist of things to check out has value to me as a consumer. The fact that that list has been through the process it has - judges nominations then fan voting - gives me confidence that, while i may not agree with every item's place on that list, in general it will be a list of quality stuff. The sheer number of people involved make it more valuable to me than a single reviewer's subjective opinion, for example.