What is the advantages and disadvantages of subcontracting maintenances activities?

There are many advantages and disadvanatges to sub-contracting. Usually work will be subcontracted out to specialist firms with specialist skills that the main contractor cannot do as well. For example in the construction industry contractors will sub-contract different parts of the work out like the masonary, cladding, floor screeders etc. They do not only do this for the best quality of workmanship however they are also passing over responsibility of the build to the sub-contractor. Another advantage to sub-contracting work out is that is stimulates the economy and keeps alot of businesses alive which depend on the larger businesses which dominate the market share. It keeps a flow of money. The disadvantages are that with the pass over of responsiblity to a subcontractor, arguments can arise when something does go wrong between the Main contractor the secondry contractor and the sub-contractor. (is the subcontractor At Fault for poor workmanship, or is the secondry contractor at fault for employing an inexperienced sub-contractor?)