When I say "old", I am referring to that the layout/route was thought of centuries ago, long before the invention of the car or anything remotely close.
London is somewhat unusual in that its streets are actually rather wide for a European city, due to urban planning regulations enacted after the Great Fire and (until recently) the willingness of its inhabintants to demolish historical buildings. Paris, Vienna, or Prague, for example, are generally much denser, not to mention genuinely medieval cities like Girona.
London is not a representation of Europe, nor Madrid. Even Paris is completely differente. Germany was full rebuild after war. So, is Europe is a mix, but roads are not the reason to not buy tractors, is utility. Tractors are for country work.