I don't understand 'Project Pan'

My friend looked at my powder and said, oh, are you doing Project Pan? No, I'm just using up my powder until it's finished and then I'll buy a new one. Is that not what everyone does? Apparently not. So it became a trend not to buy any new makeup products until you finish with the ones you already have. But isn't that just common sense? Like I thought everyone would do that. Like I get the concept of Project Pan, but I've just been doing that unintentionally. I don't have the money to be buying backups or multiples of products. But how is it a challenge for some girls to use up all of their products? But just say they'll finish their mascara, they'll go and then buy three more mascaras? Like, huh? And these girls to use up a perfume will spray it excessively so it runs out faster. But I'm like, isn't that just defeating the whole purpose? Can someone please try to explain to me the concept of Project Pan? Because I'm just not getting it. Or maybe influencers are just doing it completely wrong.