Typically orchestral musicians are paid salaries concomitant with other similarly high skilled professions, and orchestra budgets tend to be heavily subsidized. An HR department would inevitably be a substantial added expense.
At top-level orchestras this is true. For example, at the New York Philharmonic minimum pay was about $150k pre-pandemic, cut to $110k during the pandemic[1].
It is not true at less prestigious orchestras, where salaries are much lower. For example, the San Antonio Symphony tried to lower its base salary from just under $36k to just under $18k this past year[2], which resulted in a prolonged strike (still unresolved 6 months later).
There are many more less-prestigious orchestras than top-level orchestras, so most orchestral musicians don't get paid salaries comparable to other similarly high skilled professions.
Professional music is not unlike professional sports in this regard.
