Quote from traderchi128:
If they went back to fractions (which they should) the bots/HFT guys would be wiped out. With 1/16 ths and only 6 price points each dollar they wouldn't be able to play the bullshit games they do now.
If you traded then then you would notice fractions 1/32, 1/64 and I think there were even 1/128 and 1/264 or something like that. Fractions would just open another way of gaming the market which is playing the spread. Retail would be sitting on 1/16 or 1/8 spread and the game would go inside NBBO as it does today. The only think different for retail would be higher transaction cost.
Volumes may have nothing to do with HFT. Possibly all the money is sitting in treasury markets, currencies and derivatives because of the stream of negative news and demographics (aging population).