Because I can't justify paying two premium custom cases when I still am happy with my Ncase
Buying premium cases just to not use them a month or two later is not something I can convince myself of. I regret to hear that pre-orders aren't going as well but communicating that is not helping anyone and will certainly not boost sales, I'd expect quite the opposite. Though you shouldn't focus too much on pre-sales if your business model can afford to, word of mouth can be a powerful ally.
And if your case is a good product, I don't doubt it will sell. But you have to bring your product into people's minds, not just hope they'll end up finding it. Send out review samples to well-known reviewers, get as much media attention as you can, etc etc.