Why?
Because waiting your turn is one option.
Paying more is another.
Richest Queue is a public fight for position. Take #1 and you are at the front. Get overtaken and your place stays in the queue.
Some will arrive early. Some will spend more. Some will keep coming back until they are #1 again.
Every place has a history: what it cost, how many times it reached the front, how much has been spent getting there, and where it sits now.
Everyone has a place. Only one gets #1.