The example of the toilet is perfect. Good interfaces are designed to meet the needs of the user community. An expat in Japan is not a member of the community for some sense of "member" and "community". The solution for the outlying case is that the outsider asks for help. This transfers the expertise.
There's a trap and tradeoff in making an interface too clean: discoverabilty suffers.
Some users might never go beyond the simplest of use cases, but more advanced things need to go beyond that and it shouldn't be hard to find out how.
If users have to google how to do something, you have lost.
Apple is a good example of this. They value their clean and intuitive interfaces.
But I don't think they actually are. Give an iPhone to someone who hasn't used it in a while and see how well they handle things...
Because we have no traction and thus no metrics we're in a vicious "I think it should work like this so let's do it that way because you can't prove people won't like it" cycle.
There is never just one functional happy path or goal.
Each user is uniq.
Even same user expectations and 'happy' path change with time.
Take the Airbnb example, yes, at one point you just want to book a new trip.
Maybe your looking for the invoice of a past trip?
Maybe you are looking for an old booking because a friend is going to that city and you want to recommend it.
The more users, the more goals.
he's right that 99% of the time when you are looking at your account, you want the current trip. Take the 90% of the dashboard junk dedicated to "you might need this, so we're showing you just in case", and wrap it in a single, exposable "junk drawer" interface.
Or at the very least, call out the main content with styling, and make the junk more muted.
He calls this "dashboard ambush", but it's just as accurately characterized as a signal:noise problem. All the extraneous functionality is noise to 99% of use cases.
