Cars can carry much more than a bike, I can't do my grocery shopping with an e-bike.

Cars insulate you from the environment, heat, cold, rain etc. Bikes can leave you sweaty, freezing, or wet.

Rail is a complex solution. The UK has lots of rail but I'd do anything to avoid using it for anything other than day-trips. Commuting or depending on rail is a depressing experience. Granted the UK's rail network is Victorian but even with a modern infrastructure the challenges of running an efficient rail network are numerous. Some countries nail it, it's doable but I am skeptical that the UK could replace motorways with rail in any meaningful way.