Who is "they" in this case? Customers? Investors? Recruiting candidates?

In any case, I don't think this is true.

Customers don't buy a product because of who created it (in the vast majority of cases). They buy because it provides them value. Build something valuable and you'll get customers.

Once you have customers via creating something valuable, you have revenue, growth, etc. With this you can win over investors, recruiting candidates, heck even other potential customers.

Social proof might help a little, but probably not as much as you think.

If you want to start a company, you should get good at it.

Convincing founders to give you money, finding employees and convincing them to join you, marketing or selling to customers are very important skills. But they are fairly diverse and I don't think there is a lot of overlap in the skill sets.

Even just something like "market to customers" can require very different skills depending on your budget, target customer, market segment and could involve such diverse skills branding, networking, inside sales, outside sales.

I think you're right they're very important but I think devs tend to way overestimate the overlap and underestimate how deep and diverse the knowledge bases are.

Another way to think about it is: by writing comments like the one you wrote above, about the unfairness of it all, you're already marketing. You're just doing it badly.

I don't want to sound like I'm picking on you, because this is an incredibly prevalent handicap among smart tech people.