Equine Investor,
I generally avoid backing those horses, and anything else with a lot of "hype" simply because there is rarely any value to be found. The reason for this, I believe, is simply there is too much "dumb money" on these runners. You will always lose in the long run if you bet with the dumb money - but bet against it and you can take a good portion of it home with you!

Dr Pangloss,
You ask why the bookies offer Top Fluctuation - because they make money on it! If you add up the Top Fluct percentages on any given race they still add up to more than 100% (most of the time anyway) so they are still making a profit.

Why don't punters always use it? Personally I don't because I bet on longer odds propositions which GENERALLY pay better on the tote anyway (not always but on average I am better off with the best tote price). Also I don't like betting half an hour before race time which you have to do to get TF prices. If I was placing my bets in the morning on short priced runners then I would definitely go for TF with a bookie rather than TAB.