Passing our local pharmacy this morning I saw a sign saying "Covid 19 Testing Kit -----FREE ----(for those with no symptoms)

Amongst the intelligentsia posting on this forum please can anyone tell me why you would test yourself for something for which you have no symptoms?
Then ---having tested yourself and found to have the Virus it would appear that they tell you to self isolate, however, you do not seek treatment for this Virus.
Question is ---are you clear of the no-symptom virus after 10 days isolation or are you expected to pick up another FREE testing kit to see if you still have the virus? OR ---should you then seek an appointment with your GP who is probably not seeing patients face to face and they will give you the all clear by telephone?
If you still have the virus, are you then expected to self-isolate for another 10 days, again without receiving any treatment and then after 10 days are you clear etc., etc. -------ad nauseam.

I have no symptoms for Malaria ---but I can't get a test anywhere. I have no symptoms for anything at all----so why can I not get a free testing kit for my no-symptom illnesses? All a bit strange.
Norder ---you must have an answer ---somewhere!