Probably around the rise of the SaaS-ification of everything, when it began to matter how quickly you could get users to jump through the hoops into paying for

Probably around the rise of the SaaS-ification of everything, when it began to matter how quickly you could get users to jump through the hoops into paying for a subscription. Before, user conversion rates still mattered, but funding came from non-subscription sources so it didn't actually matter whether a user found the service to be useful in the long term.