Why would anyone want to pay indulgences (yes, indulgences are still officially accepted by the RCC) to decrease their time or someone else's time in purgatory? Define "pay".
"Why would you not want to help someone enter heaven sooner rather than later? The benefit of purgatory is to purify the soul an if I can help that along then why wouldn't I?"
Which brings me back to my original question- why hasn't the Pope proclaimed a "clean out purgatory" campaign? With a tool as powerful as the Prayer of St. Gertrude the Great in your arsenal, I've shown it would be easy!
Look, you can't have it both ways. Either it is good to pray to get souls out of purgatory, or it isn't. If it is good, then launch the St. Gertrude missiles and get it over with!