There are 2 things: 1) If you've been doing it for many years without any success - it's a signal for them that you're not willing to go all in or you're not a

There are 2 things: 1) If you've been doing it for many years without any success - it's a signal for them that you're not willing to go all in or you're not ambitious enough. 2) Sales and/or number of users will be the ONLY way to prove your idea for a majority of investors. They understand that it does not really matter what they think about your idea - what matters more is what the customers think about it.