Why don't cooperatives of IT professionals exist? It's a business with low capital entry and high dividends.

Workers should prefer to own their company as risks are really low (in contrast to other industries).

Worth noting that is completely legal in the USA and even encouraged by the tax code. They are called ESOPs (Employee Stock Ownership Program). An ESOP configured as an S-Corp that is 100% employee owned pays no federal business tax. Some examples of well known ESOPs in the US are Wawa, Bob's Red Mill, and W. L. Gore & Associates (makers of Gore-Tex).

Worker cooperatives are fully compatible with capitalism. Only mentioning it because sometimes this idea gets unfairly maligned due to some mistaken association with socialism or even communism. There should be more of these sorts of entities in the USA and Europe, and frankly everywhere. It's an assured route towards better conditions for the working class, by making them owners and stakeholders in a more substantial way than merely holding some stock equity (which is kind of a superficial ownership that's sometimes presented as this same type of worker cooperative ownership).