Bitcoin is not yet legally accepted in most countries, so it is not the right time to use Bitcoin as a salary. another problem is that the rapid fluctuations in the price of Bitcoin can cause problems when paying salaries.
Bitcoin's legitimacy is one reason but not the biggest one, its volatility is a more worrying issue.
There are some large companies that can implement this process if they want, but for ordinary companies, paying salaries in Bitcoin will be complicated. Companies will be more important if they can send salaries to their employees' accounts with very little cost. From my point of view, it will be possible only when the whole world accepts Bitcoin legally, otherwise it is very complicated.
Conversely, I think small companies will adopt bitcoin more easily than large companies because with fewer employees, it will be easier to handle. Meanwhile, for large businesses with thousands, even hundreds of thousands of employees like Apple, Google...this becomes extremely complicated and costly. Think about it, how much time and effort would it take them just to adjust the payroll of thousands of employees to match the current bitcoin price every month? Whereas with fiat money, they don't need to do anything extra.
I can say without a doubt that the way El Salvador is using Bitcoin, all countries will start using Bitcoin, and we may not have to wait long for this.
Don't want to disappoint you but for me, the adoption of bitcoin as a currency in El Salvador was almost a failure because the people there refused to use it as a currency.