Yes you're correct also local labour laws. One countries generous holiday package may be below the legal minimum for another.
Most companies I know that operate internationally have subcompanies in each company they have employees in. Any FTE is employed by the sub company for taxation and legal reasons. That's a high admin burden for a 10 person start-up easier just to employee people in the same country.
But another reason for hiring to be restrictive is due to taxation reasons. Companies may have constraints.
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