How about the volatility of it? Bitcoin is very volatile, this month's salary could be bigger or smaller in bitcoin value next month. Will the company shoulder all the fees when sending the salary for all their employees?
For a multinational company, this is not a problem for them, before embarking on this salary basis, they know how much they might have been generated and how much Bitcoin purchased and stored for future payments, to me it's likely be an advantage to the employee because they might have purchased bulk of bitcoin before payday, gradual purchase of Bitcoin generates more income even before disbursement.