(We currently have a large rotating LOC with a bank, but this is not always practical when you're a startup/small business getting going)
Paying tons of cash out the door to buy inventory to meet demand over X days while it sits in your warehouse is very often less efficient than paying even ridiculously high APRs on bridge loans. Cash flow is a consideration just as raw ROI / profit margins are, especially for smaller businesses.
Yes, many bridge loan issuers are preying on uninformed / underbanked people. I won't deny that. But in the small commercial space, bridge loans are used effectively, responsibly, and regularly without abuse - especially for those carrying hard inventory.