"Lenses didn't get smaller because physics says it's impossible, if you want to catch a certain amount of light you have to use a lens with a certaint size, no matter the type of lens.
Future "lenses" might get much lighter and thinner, but surely not smaller in area, you can't break physics ;)"

That is why the larger the diameter of a camera lens is, the higher speed you can use for the same ISO of image sensor.