It appears that since teams no longer have assets that riders need their own insurance as they seem to be classed as self employed.
I do not know the actual facts, but in such a dangerous sport it would be hoped they are all insured in some way.
Self-employed individuals are not typically insured by the hiring company. However, if you are a contractor or subcontractor, you may need to have your own insurance, especially if you are providing tools and uniforms. Employers' liability insurance is generally required for businesses with staff, including self-employed individuals, to protect against potential claims for workplace injuries. It is essential to assess the level of control and independence of the worker to determine if they are considered an employee or a bona fide subcontractor, which can affect the need for insurance.
www.gov.uk+5