In the UK, we mandate that certain insurances have to be taken out. You legally need car insurance – because access to the wholesale cost of repairing a damaged car or human is too big a risk for any one person to bear.

And more importantly, the likelihood of having to pay those costs is relatively high. If the risk of car crashes was low or the harm they cased was small, insurance wouldn't be required. This seems very relevant in the case of electricity supply. Electricity prices change all the time. Some of those changes are reasonably predictable, but even within that there are highs and lows and the fluctuation is pretty wide. When something outside that happens, which it will, it can really spike. Exposing individual buyers to the wholesale market rate without the kind of cap that Octopus provides seems to be pretty much guaranteeing problems for those buyers.