A modern car is a computer network with wheels. That has made independent repair considerably harder, and not primarily because the mechanics are more complex.
The mechanisms
Diagnostic access. Fault codes and live data are available through the standard port, and the detailed information needed for serious work often is not, or requires a manufacturer subscription.
Parts pairing. A component is coded to the specific vehicle, so a genuine replacement part does not function until authorised with manufacturer software. That converts a mechanical repair into a permissioned one.
Software locks on functions unrelated to safety, where the technical justification is thin.
Why manufacturers do it
Service revenue is a substantial and reliable earnings stream, and directing it to the dealer network protects it.
The stated reasons are safety and security, which are legitimate in some cases – a badly calibrated driver assistance sensor is genuinely dangerous – and clearly pretextual in others.
What is changing
Rules requiring diagnostic data to be available to independent repairers on fair terms have passed in several jurisdictions. Some also address parts pairing directly.
Enforcement is the weak point. A requirement to provide access on reasonable terms means little if the terms are set by the party being regulated.
Why it matters beyond cost
Vehicle lifespan. A car that becomes uneconomic to repair at eight years because a module costs more than the vehicle is worth gets scrapped, and scrapping a car has a large environmental cost that no amount of efficiency in the replacement offsets quickly.
Practical advice
Before buying, check what independent repairers can and cannot do on that model. The information exists in owner forums and is never in the brochure.