It's impossible to know how much to pay to get into the next block. If there's 10 payments waiting to get into the next block and there's only space for 9, ther

It's impossible to know how much to pay to get into the next block. If there's 10 payments waiting to get into the next block and there's only space for 9, there's no way they are all going into the block, regardless of their fees. Users don't want to play a complicated expensive, impossible to win game in order to get their payments processed in a known timeframe.