talking to potential customers and users about product market fit
is not a given it will work
Making a product based on your experience of a market - 25% chance it works out (of which 5% chance it will become a big company)
To that, even after talking to customers
you are only taking it to 30% chance it works out, and of which 7% chance it will become a big company
*
your hypothesis is based on data points
hopefully things like actual experience in the market
market research
seeing what sells
seeing what doesn't sell
*
Customers and users are just as likely to give you bad data (of what they THINK they will buy) or impractical data (something that benefits them and doesn't benefit you)
It only adds a few percentage points to your likelihood of success
on the other hand - seeing what customers actually BUY and SPEND ON, that has a lot of value
However, even that is a piece of the puzzle, and not the solution