It just evolved though, it was really design as a payment system. But there are individuals who I will say take advantage in the beginning and when bitcoin has a price, then it become a asset.
After 14 years since 2009, with serious losses of fiat currencies' purchasing power and with exponential growth of Bitcoin price, they found that Bitcoin is a good asset.
Nowadays, with high trading volume of Bitcoin, they can more easily to buy and sell bitcoins. Price won't be dumped if they sell their bitcoins on the market and there are OTC markets for whales too.
Your argument is invalid though, it's not that complicated, there are countries already who uses LN for fast transactions. And there are still merchants who are accepting it as mode of payment but maybe the numbers right now is not that big.
The adoption of Lightning Network is good recent years and if Bitcoin has good growth, Lightning Network can have better growth because people nowadays are more aware about Bitcoin and it is less vagueness, barriers to convince people using Bitcoin and learning about Lightning Network.
Lightning Network growth last 5 years
https://txstats.com/dashboard/db/lightning-network?orgId=1&from=now-5y&to=now