Probably because you end up reinventing unions from first principles. You start off with a group of employees organising together. Then they realise some of the

Probably because you end up reinventing unions from first principles. You start off with a group of employees organising together. Then they realise some of the things they need to do require money. Then they realise you need some contingency to pay for big expenses. Then you realise you can use your bargaining power to help members in other ways for example here unions offer lots of services, discounts and funds for things like education. We’ve also just been through a period of labour renegotiation with some strikes which has ultimately ended up with the government getting involved with promises of reform to resolve them. Plus many countries have laws surrounding how unions can operate and protections for employees organising them. In a less enlightened society employers will just lay off anyone attempting to organise. So in general Unions are typically formed explicitly because people have lots of existing evidence of the benefits.