I think the advice has to take into advice lots of different circumstances and situations.
So I would say they have given advice for the worst case scenarios - maybe someone in a shared house where all the other people are in and out and maybe working, possibly in a built up and busy city.
We have taken the chance to do a risk assessment for this, based upon our own circumstances.
So we are a family group. I can choose to go to work if I need, but that work is on the family farm 3 miles away and everybody at that premisis is also doing an extreme isolation. My parent's in law are elderly and have carers so neither I nor my partner (who lives at the farm) go in there at all.
My partner is also on the vulnerable list so he is staying in his cottage or going outside on the farm to do bits and pieces. He is having deliveries to his cottage for food. He also has Aspergers so is absolutely anal about the transmission risk and making sure that he cannot pick it up from anything. His house is now like infection control central.
So my work is not a risky environment.
My car was recently serviced and everything was sterilised on its return, and its now sitting for 5 days before I use it again. The garage picked it up and delivered it for me.
My household is on isolation apart from me going to work. We have deliveries for food and supplies. anything coming in is sterilised and no boxes pass the threshold - they are opened, contents tipped in, disposed of and then hands and knife to open boxes washed thoroughly. spray the door bell for anyone elses safety.
My son stays in or plays in the garden. My daughter then is able to mix with us as we have done everything to prevent cross infection. Its like a 2 week course on IVs extended and cranked up, so we are sort of already able to do it. We are lucky enough to live in the countryside so we can get out if needed, and the air is much cleaner. I decided that reducing our freedoms gave my daughter more freedoms, which made life more fair and doable.
And dont forget that this is advice. You need to use your own assessment from what you understand, so that you can do the best you can.