I guess kind of a similar expecation was in place for light as well - if you dim your light source then it emits less light waves.

Well, turns out if you go small enough then you see it's actually individual packets of light with certain amounts of energy where the amount of packets (photons) sent out decreases as you turn down the intensity. So, the total amount of energy outputted still matches the input, but the output is in discrete packets, where each packet can exceed the level of input energy at a specific time. So, on a large scale everything seems fine but as you go to very small energy levels it starts to look different.

I guess the expectation with gravity is that going to very small masses, some different underlying mechanism will appear. Or it may not. So they're trying to find out.