Most channels require significant lead time to yield an ROI. For example, content marketing works best over time after it has been able to yield backlinks and SEO traction.
Some channels yield quick results but not day in and day out. For example, influencer marketing can earn you quick results in terms of sales for low effort (though high cost).
But those results don’t continue occurring over time. Instead, you earn sales on a per post basis, and often less each time it is posted. Some channels are consistent but time consuming to dial in. For example, AdWords can produce consistent results for your brand, but it takes a while to master and earn specific placement. With social media advertising, you can have consistent sales coming in from the first day your website is live. For modern ecommerce sites, the ability to immediately and consistently bring in new customers is a HUGE deal. Even if you can’t achieve net positive revenue on the initial sale, referrals, email marketing and customer retention can pay off extensively with every marginal customer.