Our ancestors found climbing up a mountain quite cumbersome due to its steepness and hence would go round and round the mountain so as to lessen the effect of the steepness while increasing the amount of time to reach the summit. This indirect approach made it easier in spite of the fact that it was frustratingly longer. For particularly steep mountains this was infact the difference between success and failure because some mountains where simply too steep to maintain a direct route. Hence our ancestor drew similarities with this climbing to how to approach a person of high social standing or a highly complex issue. An indirect approach was always more rewarding.
The proverb is used as advice of how to approach a person of high standing or a matter of great difficulty. It informs that there is greater reward in a circumlocutious approach that is not direct or is assisted by intermediaries. It can also be used to calm down an impatient elder as one presents their case indirectly.