People are probably hiding their symptoms because of the strict five days of medical leave that are being given even for mild symptoms.
Not every employer is understanding. Not every job allows you to work from home on those five days of medical leave.
First symptoms can be misleading. There are many people with allergies that can cause a runny nose or throat irritation. This suggestion is irrational.
This would push people to lie about when they first experienced symptoms, which would then hinder the effectiveness of contact tracing and quarantine orders.
It is easier said than done. Covid-19 is not the first thing people think of when they have flu-like symptoms. They will wait a day or two in the hope of getting better the next day.
Wang Toon Joon