Car sales and car use bring in a lot of money to the economy, far more than bike sales and bike use. One can argue that cycling will reduce the likelihood of costing the NHS but we can't say that drivers do not visit the gym and thus will also cost the NHS less. Buying a car being in more tax revenue in terms of sales tax, fuel taxes, road tax, and a whole host of other fees (insurance for example). Then you have the parts suppliers and servicing centres which keep more people employed whose taxed salaries also contribute to the economy. Then there's the requirement for increased road infrastructure and maintenance which also bring in money and keep more people employed. I doubt politicians are quite smart enough to understand the figures in detail so they see the main points in the sense that one £20k car brings in £4k tax, uses on average £2k petrol, needs servicing annually and so on. In real terms, what does cycling really give the economy compared to cars?