What was the primary drawback of mid-20th-century mechanical bathroom scales?

Inherent inaccuracy due to calibration drift and offering no automated way to record the measurement.

Mechanical bathroom scales, which relied on a system of calibrated springs and levers to move a pointer across a numbered dial corresponding to the depression caused by weight, suffered from several significant limitations compared to later digital versions. A key issue was inherent inaccuracy; the precise calibration of the spring mechanism could degrade or drift over time due to wear, temperature fluctuations, or environmental factors, leading to inconsistent readings. Furthermore, these were isolated analog devices. If a user wanted to track their weight over time, the only available method was manual recording, meaning they had to physically write down the number displayed on the dial. The mechanical linkages themselves were also prone to wear or sticking, requiring maintenance and further impacting measurement fidelity, unlike the electronic conversion provided by load cells.