How many good - even great - unpublished novels never see a singe reader because the writers who wrote them are led to believe traditional publishing is the only valuable avenue, that self-publishing is the "amateur" or "in-a-hurry" way? There's being in a hurry, and there's not wasting the precious time we're given in a short life. If the book is good, and if it's ready, it doesn't always make sense to wait for a publisher to decide the timing is right for the market.

"More" is nice, but even with a traditional publisher, there are always "more" readers who could be reached (if the cover were better, if the publisher put more effort into marketing, if the magic of timing were on the author's side...). But most writers want to reach readers, period. No set number. Just people who will enjoy the story, or learn from it, or feel understood by it, or be disturbed by it. We no longer need traditional publishers to find readers. The internet is great for that.