Tatsiana, mainly it is driven by the wish to get somehow start of working time and duration of working time into the monitoring window (for digital tacho users), see also my request / locationGPS request on https://forum.gurtam.com/viewtopic.php?id=12378 (already got 3 people wishing it).
So the task in the above link is more importand, but in general it makes the platform more flexible to have a sensor that can have a timestamp: you can create all kind of sensors and trigger them by physical inputs or other clever notification schemes.
Example (exept the working time): you have different kind of engines / constructian mashines and want to have always on your eyes the actual status of events. At the moment you need to show sensors and a sensor can be on or off. But mostly you want to know when this sensor was the last time on/off or the first time on/off. For this you need to create a report and the report shows it.
After long discussions with existing customers my conclusion is that users just lazy and want to have all information without moving the hand/mouse/finger... So if such kind of "stati" can be shown as sensor it would make Wialon more flexible and cool ;-)
But.... More importand ==https://forum.gurtam.com/viewtopic.php?id=12378
Politeness dictates it to write his name on a post