Where I work we sell subscriptions to (mostly) academic organizations. There is no way these people will go to a web page and subscribe with a credit card, instead they talk to our sales people multiple times, have to talk to other parts of their organization to get the money, often write a bespoke contract, etc.
Similarly I have worked for systems that would sell a highly customized system to a company like Airbus or Comcast or Safety-Kleen and there would be a huge amount of work going into determining what exactly gets sold which again, is not comparable to going to some landing page and paying with a credit card.
If you're selling mattresses or something, maybe that's different.
Even figuring this out is valuable. Say I've got an idea for a hot new academic thing.
I know who needs this, I understand their pain, but its really valuable to understand their procurement process as well. If they need to have sales people as part of the process, I need to know that (and cost it in.)
Talking to my target market, and understanding what it takes for them to pay me, is a big part of understanding if I have a real business idea or not.
The difference is "consumer product" vs "enterprise products". My current employer is certainly not a startup, but I have worked at startups (angel, venture-funded or pre-funded) that worked on enterprise products.
For consumer products what you're saying may make sense, but that is not the universe of all products and opportunities.
Similarly I have worked for systems that would sell a highly customized system to a company like Airbus or Comcast or Safety-Kleen and there would be a huge amount of work going into determining what exactly gets sold which again, is not comparable to going to some landing page and paying with a credit card.
If you're selling mattresses or something, maybe that's different.