I understand why people wonder why they have to pay a general contractor when it's actually the sub-contractors who do the work. But there are a number of reasons you should want to pay for a general contractor:
When you hire a CG, you're not just hiring the GC, you're hiring the relationships that GC has with their sub-contractors. This is probably the most important and valuable thing the GC provides. Why is this important? The reason is because when a GC hires a sub-contractor, the sub-contractor is motivated to go a good job in a timely manner at a fair price so that the GC will hire them again and keep them busy with more work. When a home owner hires a sub-contractor, the sub-contractor has no motivation to do a good job, or complete it on time, or for a fair price. Even if a sub-contractor is recommended by a GC, that is no guarantee that the sub will give you the same service (or price) as they give to GC's.
When you hire a CG, you're not just hiring the GC, you're hiring the relationship and experience that GC has with the local building permit authorities and building inspectors and inspection process. If you have never had any experience in getting construction permits, or construction inspections, you might think that this should all just be a matter of following legal procedure, but in reality it is anything but that. You might also think that building inspectors would treat you the same as they treat licensed general contractors, but that isn’t always the case. Suffice it to say, applying for a building permit, and having the construction project inspected can be like going to court without an attorney. It’s not impossible, just a lot more risky.
Another important thing the GC provides is project scheduling and management. Work and events on construction projects has to follow a strict sequence. You cannot expect sub-contractors to be conscious or aware of this, or to advise you or take responsibility for it. Everything out of their sphere of work is not their responsibility, so they cannot be expected to take responsibility for it. For example, if you hire a drywall sub-contractor to install drywall, they’re going to come and do it regardless of whether you have had all of the inspections you’re supposed to get before the drywall is installed. If you don’t know what inspections need to be done, and take responsibility for getting them done before the drywall is installed, then the building inspector can require you to have the drywall removed so that the inspections can be made. You will be responsible not only for having the drywall removed, but also for having it re-installed.
Sub-contractors also cannot be expected to take responsibility for making decisions or judgements about how the work they do might affect or interact with the work done by, or materials installed by, other sub-contractors. Construction projects contain hundreds of examples of this, and only an experienced general contractor can be expected to anticipate or be aware of these sort of things.
Sub-contractors also cannot be expected to be aware of, or take responsibility for, building code implications for decisions they make, or work that they do. For example, when the plumber installs plumbing for gas lines, they will install the plumbing to the gas meter wherever you tell them to put it, but you might later find out that code requires the meter to be placed somewhere else.
The GC is responsible for all of this, and if the GC fails in managing all of these details and logistics in such a way that it ends up costing more, or delaying the project significantly, then the GC can be held responsible for it. Without a GC, then it’s all on you.
Another important thing the GC provides is quality control. Not only is everything outside of the sphere of a sub-contractor’s work not their responsibility, but some sub-contractors do not even take responsibility for the quality of their own work. Some sub-contractors will assume that home owners are not going to know how to judge the quality of their work, and since you’re not going to need to hire them again, they really don’t have a lot of incentive to do a good job for you. But because they know the GC knows the difference, and they know their next job could come from the GC that hired them, they’re going to want to go a good job for the GC.
Another thing the GC provides is protection against legal liability for personal injury of workers on your property. If a sub-contractor gets injured while working on your property, and you don’t have all of the appropriate insurance in place to cover it, you will be personally liable. This is another one of the important things that a general contractor provides for you.
So, the question is, should you be your own general contractor, or is it worth hiring one? It’s up to you, but consider the points above in your decision.