We want to use nanomaterials because nature uses nanomaterials. Some of the most interesting effects and behaviours in nature are because of nanoscale structures. The reason why butterfly wings and peacocks feathers have such brilliant colour is because of nanoscale structures, the actual colour of the pigment they have is brown, but the nanoscale structures causes the light to be scattered in all those brilliant colours!
On the top you can see images of the butterfly wings, and on the bottom you see the structures researchers are trying to create to get similar effects!
The lotus leaf has amazing super hydrophobic properties which is again because of the structure of the surface
These are just 2 examples of how nanomaterials are used in nature.
We use nanomaterials for all kinds of things, the processors in computers and phones are developed using nano-sized transistors.
Here is a website which gives lots of uses for nanomaterials, let me know what you think , which one was the most surprising? https://www.nano.gov/you/nanotechnology-benefits