Having said the above, I also agree with the point that "unwillingness to spend Bitcoin by Bitcoiners is also the cause"

However, it is relatable why this is the case; Bitcoin is the hardest, scarcest monetary asset in the world, with price volatility.

The volatility of Bitcoin is the common ground for which both merchants and Bitcoiners might be reluctant to accept and pay in it respectively.

Most merchants run on Fiat, accepting and holding Bitcoin means possibility that their Fiat capital dips following a Bitcoin dip, and for Bitcoiners, nobody will be happy to spend their Bitcoin when the Fiat value is down, especially if they acquired such Bitcoin when the Fiat value is higher.

So the ultimate solution is making Bitcoin the base layer for moving fiat value. This helps the merchant accept Bitcoin confidently, and also ensures that any Bitcoiner can pay with Bitcoin at any point in time.

One of such solutions is "Fiat Channels", a lightning protocol specification that enables the creation of synthetic assets on Lightning. There are several other implementations like this such as "Stable Channels".

With these protocols, merchants could accept Bitcoin while retaining the "stable" Fiat value of the Sats as at when received.

MoneyGadger may set up a Host and offer these services to her clients, ensuring that Sats continue to exchange hands while carrying Fiat values across.

Fiat Channels: https://github.com/standardsats/fiat-channels-rfc