We realized early that you can have all the tactics in the world but if they hit your homepage and your homepage is bad, it’ll go to shit. If users sign up and you don’t have them doing anything useful after that, it’ll go to shit. If they go through onboarding and your onboarding sucks, it’ll go to shit. If you get it all right, they’ll become a happy customer, at which point your new obsession becomes keeping them. If you don’t keep them, they’ll either leave or go to another customer which means, again, it’ll go to shit. If there’s one point you should take from this, it’s that you have to work very, very hard to stop it all from going to shit.
Emphasis mine. There are so many points in the customer journey where everything can just fall apart.