Apart from their not NHS contributions as National Insurance isn't a hypothecated tax

It's the closest there is to 'medical insurance paid by employer'. OR what do you think grandparent means when they say 'if the self-employed person can’t afford their own insurance, but their employer doesn’t fund it for them'?

The gig economy isn’t just an issue in the UK – the example I had used was Germany (which I had literally mentioned in my original comment), where exactly that is happening.