There are lots of reasons to start your own online bookstore. You may be self-publishing in print on demand or POD, so that you have copies of your books for sale. Or, you may have a publisher who has gone bankrupt or closed its doors, so you’ve purchased boxes of books that you’d like to sell. Or, you may have purchased author copies somewhere along the line that you’d like to sell and get out of your basement.
I’ve had all of these experiences.