"Why meterless cameras are important to photography"
There isn't any importance of "meterless" to camera. But it is the light meter that hub and the starting point of your photo creation. As the medium of the photography is the Film and the idea of the photography being Painting photo with light You need a photo pallet to mix the paints to create a painting. Films coating chemicals are based on a light sensitivity that is recorded as ASO or ISA. If a film dose not need a particular meter /light controlling the end result is highly surprising. Any film out of any protocol of exposing to gain into a printing zone is a hit and miss effort. Using the sunny 16 rule means without meter doing / exposing a film USING AN ALTERNATIVE WAY of light reading before making photos.
So light metering / and controlling it to create the image TO MAKE IT NEED SKIILS. If you do the pinhole photography it needs metering too and that is why they soul be on stands for hours before accomplishing the shooting.
light Meters are very helpful and they will facilitate to work faster and get consistent results on you photography. If keep your time free to make photos.
If you believe you can make photos with out meters you'll never get a "right photo" negative printed on a wet print under an enlarger in any instant. Exposing a film in a camera and printing a photo is the same revers act in photography.
Zone system is the main principle that is used in photography and it must be well employed and respected in both cases. Exposing a film or exposing the photo paper under an enlarger before you attained a good result.