I went to a business networking event last night and got into a very interesting conversation with someone who is not in the home/building or interiors industries. She was asking me who I worked with on projects and I mentioned that I bring in people as needed - builders, contractors, architects, trades,etc - as the project required. Surprisingly (to me), she didn't seem to think this was the right approach - that it would somehow limit my client prospects. Her issue was that if a homeowner had their own trades - an electrician, for instance - they would be put off that I would expect them to use my own people.
My reply was that I have had clients use their own people and more often than not, the work isn't done to my specification. Even when I've supplied detailed sketches (as above), the contractors don't necessarily follow it because they aren't working for me. So, I've not only not ended up with the design I specified, but the client hasn't gotten what they paid for either.
Several years ago, I worked with a lovely client and specified the backsplash design above. The clients purchased all the tile but their tile guy convinced them to go with an easier (for him) design. This same tile guy convinced them not to use the 1" glass tiles I'd recommended be chipped into the corners of the basic 12" square ceramic tile flooring going into their very small bathroom. It was an easy detail that upped the look of what was a very modestly priced floor.
It would have looked something like the above (only tumbled looking ceramic tile with moss green glass tiles.) But, again, the tile guy convinced her that the glass tile would break (even though it was made for use on a floor) and they should skip it. Really, he just didn't want to do the extra work and make sure the subfloor was level.
This isn't to simply cast blame solely on the contractors either, it's really not. I've had clients who had their own builder in place when they hired me to help with the decorative details. We'd selected and purchased all the lighting and it was in house when the electrician was ready to install. Unfortunately, my client was traveling out of the country at that time and her partner either wasn't aware of the design plans, or cared all that much, and the electrician wasn't given proper direction. So, lights were put in the wrong spaces, recessed lights weren't installed as expected and a ceiling light (that was meant for the laundry room) was mounted dead center in their library.
The point I'm trying to make is that when a designer wants to use their own resources, it's not just because we are control freaks (or are making some kind of backroom commission). Well, okay, we might be control freaks and we might have an arrangement with certain tradespeople or vendors, but it's not only that. In the end, we take our role seriously. We're hired to create the best design possible for a project and we can't guarantee delivery on that if changes are made after our designs are submitted. Our design work is only the start of the project, it's all in the execution.