If I isolated, I'd get nothing - I'm self employed so I wouldn't even get SSP.
I'd have to refund clients, and certain clients might go elsewhere and simply not come back afterwards. If we're talking about some of my larger business clients, that would have a serious long term effect on my business.
And to add insult to injury, I wouldn't even be allowed out to walk the dog so I'd have to shell out for a dog walker every day. He has issues and is not the sort of dog that can be walked by just anyone.
I cannot trust that I'd get the £500 self isolation grant either - I'm not on benefits, most people who aren't on benefits get turned down, and as one of the Excluded who was denied SEISS, furlough and UC despite losing work, I've no faith in the system whatsoever.
So my cost of living would go up, I'd have not one penny in income, and I'd risk a long term detriment to my income. Weirdly, I haven't downloaded the app, and I wouldn't self isolate because it's just not affordable for me.
In years to come analysts will think it was mad that they paid some people to stay at home when they didn't really need to (furlough etc)., but refused to support people like me to self isolate when they really did need to. It's a bizarre set of priorities.