If it is a site wide coupon, it is usually sponsored by the platform. Their play is either user acquisition or some quarterly targets on gross volume. This is l

If it is a site wide coupon, it is usually sponsored by the platform. Their play is either user acquisition or some quarterly targets on gross volume. This is likely in early stage ventures who burn VC money in order to boost their perceived valuation. If it's a seller specific coupon, it is usually sponsored by that seller. This is likely in cases where the platform is mature and relies on cash flow to sustain. Sellers can't piggyback on free marketing from the platform and need to spend money vying for attention on the platform. Although in either case, because there's a shared interest, it could be a joint sponsorship with both platform and seller sponsoring a certain portion of the discount based on agreed terms which can vary from coupon to coupon.