Central planning and allocation of goods

I often hear that central planning doesn't have the benefit of price indices to know how much they should allocate their labour and resources, so they have to make estimations, causing inefficiencies. But that doesn't make sense to me because every private company has to do this as well, right? When a company is created, they sell their commodities for a base price and adjust their supplies according to demand. Why can't the government do this as well?