At least, when you are building it yourself you can toss substandard parts or wood, ARFs, you have to take the crap wood they build with or stick patches where they might do some good. I have been doing ARF planes for about 20 years and have decided that you really don't save any time OR money going that route. The first warbirds I built in the early 70's were kits or fiberglass and foam, so I am familar with the methods used in construction. The fiberglass fuse planes I have built in the past never had panel lines for reference. My brother has scratch-built planes with large 10 foot foam wings before there were giant scale kits available. One, we used to kid him about, we called his wing a surfboard. He crashed it straight down into the woods and the wing was not damaged, just knocked off. He used to visit the small engine repair shop, buy weed-wacker motors that had been tossed into a bin for a few bucks, take them home and get them running to power his own-design giant scale planes. He did not have much horsepower to work with, but they flew.
It is always nice to open a box and in a few minutes have a plane that looks ready to go. Only they usually require extensive mods. to make them airworthy, and, tossing out the hardware supplied with the plane and buying all new stuff is like paying twice. You could argue that you should just use what comes with the plane and save money, but that has led to costly failures and loss of a lot more than the ARF.