Because even though there are 300,000 - 500,000 new consumer products launched in the U.S. each year, 99% are generic commodities like a new kind of 2% milk or whatever. The number of new products that are actually interesting is very small, which means that there is a very high cost of discovering and reaching out to enough of these product makers to make the site viable.
C.f. why I shut down my previous startup: https://www.fwdeveryone.com/t/-Gk8HmiRSZ-mrUxE0rH3SQ/deadpoo...
It's definitely possible to do something successful in this space, but not as a bootstrapped startup. The AngelList acquisition makes perfect sense, because they can share the cost of leadgen while creating the opportunity to meet a wide range of founders' needs. There is a big opportunity here if someone is able to come in and execute a rollup and IPO, but those are extremely tricky to pull off.
