Not OP, but I can think of two reasons – too many LEO satellites can actually hinder views of the night sky[0] and additionally, the risk of kessler syndrome[1].
I'm in no way equipped to give a scientific risk assessment of either, so I'll defer to others to share if they feel it's major concern. But whether these are present issues or not, they're worth considering and thinking about as we move forward with more LEO deployments. The latter issue especially, given that once it occurs, it'll be extremely difficult (nigh impossible?) to rectify in short order.