Increasing retention to infinity (and beyond) is Very Important for SaaS. It's generally easier to continue selling to an existing customer than to go out and find new ones.
It is not identically important for all businesses. (...) There are lots of specific situations where you'd do well to turn your back conventional startup wisdom and best practices.
Indeed. There are no best practices in startups. Dogma be gone. This is why uncontextualised, generic advice is so dangerous.
Rob goes on to outline two common kinds of businesses which should not try to drive retention up. Read it here.