Employer NI is a scam anyways - some government or another needed more money, but didn't want to piss off the populace by raising taxes, so they increased taxes

Employer NI is a scam anyways - some government or another needed more money, but didn't want to piss off the populace by raising taxes, so they increased taxes "invisibly" - you still get paid the same (as specified in your contract), you're just suddenly more expensive to the employer. Also, if self-employed people pay less tax than employees, that's not their fault. Again, it's a tax avoidance scam primarily perpetuated by the government (guess why? so that the lawmakers and/or their proteges can pay less tax themselves!). People respond to incentives, as they should.