Well think about it. Point of all the gears is to keep the engine right in the sweetest spot it can be? So have an infinitely variable CVT do just that. Yeah, the car sounds like a snowmobile but, the engine is always right at its peak performance when you're flooring the gas pedal.
Granted, the geared CVTs are not quite doing that, which is a different thing.
Also for a bit of trivia... the Williams F1 team back when Mansell was around tested a CVT and it was markedly faster than a conventional gearbox. The FIA banned them.
Yeah Damon Hill tested a CVT for Williams in F1 in 1993. It was the next step on from a semi-automatic transmission at the time, the theory being no lap time is wasted shifting gears with the engine disengaged from the driving wheels, plus the engine was kept in the optimum power band for longer (may be constantly I can't remember). John Barnard had introduced the semi-automatic transmission in 1989 for Ferrari for similar reasons - to reduce the amount of lap time spent inefficiently shifting gears with the engine disengaged.
As TonyJZX said, the FIA banned it before it was raced. To stop spiralling costs and less input from the driver in driving the car at a time when more and more automated systems were being introduced by the top teams.
These days the teams have seamless shift gearboxes with (dual clutches?) to achieve the same thing - lap time reduction by minimising lost time shifting gears.