TL;DR; Loot spots would have to be made visible to all players to make it more competitive to merit the addition of a leaderboard.
The only problem with a looting board compared to a bug board is that Looting Spots are specific to each player, meaning so long as they dived on every spot, they would get loot. Because of this, every player would have an equal chance (unless you fail to react in the window to press dive again, but that's besides the point) of obtaining loot as no other player could effectively "loot" it from you.
Bug Catching works different and would be able to cope with the competitiveness that the addition of a leader-board would bring as all players can see all bugs. Therefore you could have 5 people chasing one bug to get them those precious points to get into rankings on the board.