There is plenty of value left because most of the systems people use DO NOT WORK in the long run. Also for every punter using a logical selection system there are probably 10 just playing "follow the favourite" or betting on the "hot tips" from the newspaper/sky (which is pretty much the same as betting on the favourite anyway)!

Remember that over 90% of TAB punters lose money in the long run - you just have to be smart enough to get some of that money off them.