Employment contracts are protected under the labour laws and civil contracts are not. It's super rare in Poland good change.

Of course though, this is not the real reason neoliberal government is considering it. Real reason is that will pad up the retiremt system which is used more as a source to plug in the budget hole. The same move for the same reason was done years ago by PiS for Polish workers and it improved situation for both workers and budget (situation was so bad back then that around half of Polish workforce was "employed" on civil contracts, most of them with violation of multiple laws)