Oncall shifts should not exist and their ubiquity is the most clear cut sign that software developers need a union.

No software developer should ever be responding to issues outside of their regular working hours.

If 24x7 support is actually critical (hint: for most products it absolutely is not), then staffing weekend and overnight shifts to provide that support is also critical.

If a company isn’t willing to do that then they’re really admitting that after hours support isn’t actually that important.