I understand the point you are making but I find that I can't agree with it.
From what we are being told, this virus could be around for a while, life still has to go on. Exactly how are you spreading a virus by popping in to purchase a can of deck oil? I'm assuming that appropriate distances and the such like are adhered to. You're supporting a local business, in just the same way as purchasing bread. I make my own bread so could argue that bread is non-essential whereas deck oil, which I can't make (sump oil and kerosene does work but....) has to be purchased.
I think we have to very careful just how much basic liberty and common sense we sacrifice to this. Why would you uphold a fine for a driving lesson 30 km from home? How are two people in a car spreading a virus, unless they are actively sneezing out of open windows? I understand the need to keep it simple in order to minimize enforcement but a bit of perspective is in order and when they start penalising people (as opposed to a chat and a warning), for activities that do no harm, I start hearing alarm bells.