Weight: system more important than sensor size?

I started looking at m43 as a safari weight saving system. And in that case (long telelenses) I think is a very nice solution.

So I started looking at the "normal" lenses as well, since now that the new m43 sensors aren't that bad at higher ISO (even if still 2 stops worse than the new FF, you can't beat physic laws...), this system looks very interesting...

BUT

It seems to me that the weight saving has more to do with the what people want from the lenses, more than the physical issues that come from designing a lens for, say, FF.

What I'm trying to say is that people using m43 value more the small size/lightness of a lens compared to, say, a FF user; and lens designers put more effort in producing small and light lenses.

Example; given a FF setup of:

Zuiko 21mm 3.5 (180g) (manual focus)  length: 31mm

Canon 40mm 2.8 (130g) length: pancake

Nikon 100mm 2.8 (215g) (manual focus) length: 57.5mm

You can see that even fast, FF lenses can be small and light.

Yes, comparable m43 lenses are lighter (example: 45mm 1.8 has the same DOF of a 90mm f3.5, and you can shoot at ISO 400 on FF when you're shooting at ISO 100 on m43, so you can say that is very similar to the Nikon above), and in the example of the oly 45mm vs 100mm nikon can be half the weight. But half the weight of 200g is nothing. The huge gain is when you compare with regular, newer lenses on FF: the 100mm f2 is > 400g. (yes, it's f2 compared to f3.5 when it comes to DOF and noise-wise exposure, but still...).

Bottom line: lenses for FF could be smaller, but people using FF don't value the size that much, so smaller lenses are not created???