[Question] Why <scene>element doesn't have 'rain' or 'snow'

The title says it all.

I could see fog and cloud element in 'scene' element'. But there is no properties for rainy or snowy environment.

Because it's hard to present(render) an effect on gazebosim(Ogre3D)?

Start by reviewing how the `scene` element represents fog and clouds in SDFormat, then trace whether rendering is handled by Gazebo or Ogre3D. Determine whether rain and snow require schema properties, renderer support, or both, and document the reason for their absence and the scope of any proposed change.

Written by the indexing model from the issue text.