It has been this way since around 2106 when the full Etsy Payments system was bedded in. Prior to this, sellers would take all their money out each week and at the end of the month they had a big bill to pay for Etsy fees and charges. Many would forget to cost that into their pricing, and that big payment at the end of the month would take them by surprise (what you don't see you don't worry about, until it hits you in the face). Since EP began, Etsy takes its fees as you go, so for many sellers there is no need to make a payment at all, unless the timing of sales and bank transfers leaves a negative balance at month's end. You can go into the red whenever needed throughout the month, and if you still have a negative balance at the end of the month, you can pay it then, but it is usually a much smaller amount to have to pay. This way Etsy has less individual deposit transaction fees on their bank accounts and when you transfer funds to your bank, you know it is all yours and there is no nasty surprise at the end of the month.
If you have ever had your work on consignment in craft stores or gift galleries, that is how it works there. The store takes its fees out of your earnings, and you get what is left. If they charge a space rental, and you have insufficient net earnings during the month to cover it, you have that bill to pay at the end of the month.
