You are right about FLAC, when I refer to RedBook CD that includes the likes of 16 bit 48 kHz ALAC and 16 bit 44.1 kHz FLAC.
Internet contracts are very expensive. In the USA about double the cost we pay in the Netherlands.
I am pretty certain that most people do not upgrade their streaming service to FLAC HD or any other data heavy format because of risk of clogging their internet connection, data storage and home network. As important we Audiophiles rate music: In my case, High Res is not worth it. Even the chance of, my wife, my son, my daughter risking a poor MS Teams connection. Or risking complaining children because they might be running into time lag issues when they are gaming, or streaming YouTube or Netflix, no thanks.
People living in congested habitats, such as cities and highly populated areas/countries like Netherlands or strategically important areas might enjoy and can afford 400 Mbs internet. But a large amount of people still don’t have that.
Furthermore high data transfer rates are never guaranteed. We have fibre glass, 1000 MBs connection but a 100 Mbs contract. On an unpredictable time basis speed sometimes drops to half. We are multiple data hungry users in the house. Bandwidth is still an issue. To safely upgrade to High Res streaming I indeed would need to upgrade to 400 Mbs. That is at least 20 to 30 EURO extra per month. With MQA I can enjoy high res Paradise Radio and have money left to buy music.