Getting extra fuel right all the time is like expecting to play the stock market and always buy at the troughs and sell at the peaks, it doesn’t happen in real life.
Amazingly, the time and fuel used in avoiding weather is never questioned, I’ve gone over 100 miles off track before and never had it brought up by management. Not injuring and traumatising the pax and not over stressing the airframe is something they don’t seem to mind.