Because lightning uses Bitcoin's blockchain, which is the most secured (as in energy) and the most common (as in market cap) and probably the most accepted as in regulation. Plus, you can use bitcoins taproot asset protocol to issue stablecoins and send them over lightning. No other blockchain needed - which in my opinion, renders monero obsolete or at least a very niche product.
Because lightning uses Bitcoin's blockchain, which is the most secured (as in energy) and the most common (as in market cap) and probably the most accepted as in regulation. Plus, you can use bitcoins taproot asset protocol to issue stablecoins and send them over lightning. No other blockchain needed - which in my opinion, renders monero obsolete or at least a very niche product.