Even if you think what you would say is obvious, please add. This is genuinely something I think makes sense regarding local bus routes given the longevity of light rail and how infrequently routes change, but I also suffer from confirmation bias, so I’m hoping for reasons this would be a terrible idea but obviously would prefer reasons it would be an even more amazing idea than I thought.
I’d seen quite a few pictures and video of them, but the first ones I actually got to walk around and ride on were in Heidelberg in Germany. The north lines (5, 21, 24, 26) have grassy tram sections.