Or people learn and see that they can make a happy path of 90%. Or the business removes an implemented unhappy path of 5% that fails 50% of the time. Or the bus

Or people learn and see that they can make a happy path of 90%. Or the business removes an implemented unhappy path of 5% that fails 50% of the time. Or the business introduces a new unhappy path to go with the times or times just change and the happy path is now only 50% of the cases. You're completely correct. Software needs are easy and hard, and times change.