The reason sidewalks, roads, and transportation in general take such a big part of a state budget is that the companies providing these services need to adhere to the cost-efficiency mechanism, therefore there will be crappy streets that need to be rebuilt every few years. If we were to build in the most efficient and optimised manner, where the criteria were maximum efficiency and strategic allocation of resources, not profit, we could unleash such an incredible abundance that humanity has never seen before, nor can many people even imagine.
Profit makes companies create crappy, shitty products, using highly inefficient and wasteful methods, due to the structure of the market.
Actually, the reason for THAT is because a lot of local governments have either unions or contracts with monopolies that prevent those governments from doing business with anyone else. Thanks to that, these companies can do whatever they want, including building crappy infrastructure that costs too much and needs to be replaced often. You're essentially describing an unnatural monopoly that has nothing to do with a "free market," and would likely be a problem in RBS as well. Places without those problems work like the rest of the free market: those trying to sell the cheapest crappiest stuff to make the most profit end up losing out to those who can sell better stuff at the same price. In a free market perfect competition environment, profit is usually close to 0, with the most efficient producer who can make the best product winning the race. So, in places like closed or private communities wo hire their own companies, or toll roads not subject to using government contracted workers (i.e. those working with a free market) usally have much better quality roads ad sidewalks for not much more money.