A smaller F-number can make a big difference in how much light reaches an imager.
For example, the difference even between a f/1.2 and f/1.0, which may seem very close, can be significant, as shown by our F-Stop Calculator:
However, almost all megapixel cameras use lenses of at least f/1.2, with many at f/1.4 and even some lower cost ones at f/1.8 or higher.
We recently bought a F/0.95 6MP rated lens from Hikvision (the HV0733D-6MP). This lens is huge, shown below in the middle surrounded by 'normal' size megapixel surveillance lenses: