If someone is going 10s/lap faster, they will steal a lead over the rest and within a few races (until the other cars have caught up), they will kill the championship race.
The FIA has to ensure that viewing audiences are kept high. This means that they want to create an entertaining race that casual, as well as hardcore viewers will be interested in watching.
If a team wins the title by race 12, the remaining races, may take a hammering in terms of audience figures.
The FIA has a history of trying to prevent 1 team dominating. They tried to stop MSc/Bennetton and then Ferrari/MSc from dominating by changing the rules.
They also brought in DRS and made to order Pirelli tyres, to provide a better spectacle.
The last thing they will want to encourage is a team creating a car which can go 10s/lap faster than the competition.
They need to keep revising the rules, in order to keep corning speeds down. If memory serves me correct, this attention to safety all kicked of when Senna and Ratzenburger died in a single race weekend. From that point onwards, on the grounds of safety, the FIA have been doing pretty much whatever they liked.