This is a misunderstanding on your part as the system was/largely still is simply different There was no government mandated minimum wage but the pay in sector

This is a misunderstanding on your part as the system was/largely still is simply different There was no government mandated minimum wage but the pay in sectors is negotiated and fixed by negotiation between employer and employee representative organisations per sector. The rise of new kinds of pay models to undercut these systems fueled a push to in addition introduce a minimum wage. For most places the minimum wage does not replace the negotiated rates but just covers sectors for which there's no negotiation system.