A very common example of this is people suggesting to remove private profits from the modern economy. It seems like a really good way to cut down waste and save costs in theory, but it never worked in practice if you do it for the whole economy. It does work really well for some problems, but for many others those private profits seems to be a necessary evil for the system to work well.

What those people are missing is that private profits is a really good instrument for allocating resources and performing quality control efficiently in many sectors. Removing those means you now need to manage all those resource allocations and quality controls via other means, and so far we haven't found anything better for most business to business supply chains.

Governments often do well in the business to consumer space though, as in many cases cutting costs there means consumers gets worse service. But in the business to business step both sides wants to push costs to each other, so they negotiate on who should do what to make both earn money, or they will go and do business with someone else.