Decade (non plural) barring economy meters 2 rates for gas and electric were brought in just after the gas and electric market opened up in 1998. This was to say that there were not going to be any standing charges. Some companies still stuck with single rate tariff and standing charge just before 2010.
Single let rate has come back, as you quite rightly said the regulator (Ofgem not Ofcom by the way ) said it was too confusing.
Scam is also a strong word to describe tariffs, but we all know the big six (well excluding NPower as they are skint) make a profit, but when I worked for BG the only people that they/companies made a profit on where people not in debt, and the profit they made on average per year per customer was just a shade over £5 for a duel fuel customer. Although Centrica made over a billion in profit the BG arm made a small contribution to that, and the bulk of its profits (BG) came from the services side of things (boiler breakdown etc)
We all know that you can get cheaper energy away from the big six, but there operating costs a minimal compared to the big six, hence why the obvious larger tariffs. But consumers won't take a punt on the smaller companies, if they did, the market would be even more competitive.
But I agree with your statement of it being a scam on it makes no difference when it is made, but on the other side of the coin is those storage heater systems are horrendously expensive to run hence the 2 rate meters.
Alas, whatever way you look at it, energy prices are still high, but I think maybe still lower than in 1998. But you cannot cut them with massive impact and monumental job losses.