Because once they get involved they're often not worth picking up.
I think there's a lot of stuff out there that would provide value to both parties if they could simply connect. Something like Gumtree or Craigslist is an attempt to capitalise on this.
e.g. I have a broken machine. It'll be useful to someone for spare parts, to fix and resell (or for fun), as a placeholder (since it sort of works) until they get something better. I'd probably give it away. But dealing with all the time wasters on such platforms makes me want to just toss it.
It's similar for some ideas where there is definitely profit to be had, but simply connecting with the customer, convincing them that it will help them, convincing them you're actually honest, etc etc, all costs more than it's worth.
2) Being savvy at online marketing means you probably were able to figure out that the cost of customer acquisition was higher than the price people would be willing to pay for the product
The reason businesses do inefficient things is because humans are stupid habit-driven animals. To break them out of their habits, you have to assault them with expensive messaging and literally shake them until they realize you have built a better way.
