Why do we use time as our constant?

There are natural rhythms but we appear to ignore them in preference for rigid structure. Why have we lost the ideas and concepts humanity developed before our iWatch and Fitbit? When did time become our base for measurement and not rhythms? Indeed are rhythms important?

“Time”, not spacetime, for us is fixed in chunks and measured by the universal “per second”, with 1 second set by a cesium atomic clock, which are so accurate they will not drop 1 second in more than a billion years. But life is not like this and whilst time and distance are related, as is the need to have leap seconds to adjust for the earth's rotation, our life patterns are not as stable as the seconds we measure against.

Where is the link to data and our digital life?

We measure everything to the second and believe that with this measure, the data is correct. This data becomes our digital life clock and measurement rod. The point is that we have created a super accurate measurement that we live by but this measure may not truly reflect who we are or what we do?

We don’t sleep the same every night (place, partner, clothing), we don’t eat at the same time or the same thing, we breathe different air every day and meet different people. We expand and contract as we live. There is an average temperature range, average heart rate, average respiration rate, average resting rate, average walking gate, but they all vary all the time and are rhythms, which we don’t measure.
We believe in data but data is not always as good as we hope! Forever we have been told the average body temperature is 98.6 F or in range [36.5–37.5 °C (97.7–99.5 °F)] however as this article explores this might now be incorrect due to the lowering of infection and inflammation since the original work was done. Indeed we assumed that resting heart rate was within a small range but FitBit data shows otherwise. The data and the measurement might not be a good signal. If our algorithms are based on data, we have better be sure of the data and the analysis/ insight we seek

Therefore, why are we measuring and holding to seconds, minutes, hours, days, weeks and years which are not naturally fixed or firm. We look at sleep cycles but not awake cycles. Why not measure pulses per breath? Breaths per sleep cycle, breaths per awake cycle. Food per moon - even wax or wane !
What more would we learn about ourselves by thinking about data based on rhythms and not by fixed increments of time?