Regular days of rest existed in religious practice long before labor law produced the weekend. The older forms were structured differently, and the difference is instructive.
Timing was collective rather than individual
A Sabbath is observed by a whole community on the same day, so the pause is shared and social obligations pause with it.
An individual day off does not have that property. Others continue working, messages accumulate, and the surrounding world does not stop.
Collective timing is what makes rest genuinely restful, since the cost of being unavailable falls to nearly zero when everyone is unavailable at once.
Prohibition did the work that intention cannot
Traditional observance is defined by what is forbidden rather than by what is encouraged, and the boundaries are explicit rather than left to judgment.
A prohibition removes the decision. There is no weighing of whether this particular task is important enough, because the category is closed.
Modern attempts at rest rely on intention, which must be re-exercised whenever something arrives that seems to warrant an exception.
Preparation was part of the structure
Observance requires anticipating what will be needed, since the prohibitions cover ordinary provision as well as work.
That preparation forces a weekly review of what actually needs doing, which is a planning function most schedules lack entirely.
It also creates a definite beginning, marked by a time and often by a ritual, so the transition is an event rather than a gradual slowing.
The weekend is a different institution
The modern weekend emerged from labor organizing and industrial scheduling, and it is defined by absence of employment rather than by presence of anything.
Being undefined, it fills with errands, obligations and the work that did not fit the week, which is why it often fails to restore.
It is also increasingly staggered across a service economy, which erodes the collective timing that made shared rest possible.
What secular versions borrow and drop
Practices like a screen-free day borrow the prohibition structure while leaving out the collective timing and the tradition that enforced it.
They work better than vague intentions and less well than communal observance, which is consistent with which elements were kept.
Whether the religious content is separable from the effect is a genuine disagreement, and the traditions themselves would say it is not.