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Nothing goes on the layout straight out of the box.
This is the way I feel as well. IIRC, I have a grand total of 7 RTR cars out of my several hundred.
I feel that a kit is superior to RTR, because you can build it to any level of detail desired. I don't put things on my kits like airhoses, as I find that these are generally the first "fine" detail that gets broke. I also don't install uncoupling levers, as they are the next to go.
Several have stated that they don't have the skills to put together a kit.
Hogwash! There are still several makers of what we used to call "shake the box" kits. Accurail, Bowser are the main two left for these simple kits. More difficult ones are available from Red Caboose, Tichy and others.
Many of the older manufacturer's kits are still available from Ye Olde Huff & Puff, and Labelle. There are many resin kit makers out there as well for the ultimate kits, like Westerfield, Funaro & Camerlengo, Sunshine.
For many of these kits, if you've ever assembled a plastic model of a plane, ship, or car, you have the basic skills to build any of kits mentioned.