There are plenty of reasons. Companies who know what they are doing in this field are using commercially available lights. We are not simply going to the box stores and buying them on sale the day after christmas. The lights we use are a completely different quality than what is sold at HomeDepot or Walmart. I know that I can hang a new string of lights 30' up on the peak of a customers roof or 40' up in an oak tree and there is very little chance that I will be getting a call back for any lights out that first year. That the second year, a few bulbs might go out, but more than likely not enough for the customer to notice and give us a call. You can't say that about the lights from boxstores.
Now think about the fact with a customers lights, you have no clue how old they are. The customer might tell you he bought them last year, but they may actually be 3 years old. People drive by and see your company hanging the lights in November, come Christmas there are five full strings out. Now the neighbors think you hung crap.
We have used some of the customers decorations, but will not touch anything previously lit. We have installed our own lights on their garland and wreaths, but prefer to touch strictly our products. Even other commercial products that a previous contractor sold and hung for them, we wont touch it.
How we equip our selves to install so much decor? We start advertising early in the fall and then increase our advertising substantially as we get closer to Thanksgiving. We purchase from a number of wholesalers. By mid october we have a number of new contracts signed and place a large bulk order of wreaths, c9s, minis, etc, we also figure in an extra percentage for jobs we figure we will still get. Then during the rest of Oct and Nov we place weekly supplement orders.
Really the biggest thing about it, that I probably could have answered this simply with, we show the customer a sampling of the products we sell. The products pretty much sell themselves.
Why do people not respect us as they do other tradesmen? Because every Tom, Dick, and Harry doesn't think he can be a plumber or electrician!