Let's break down a good sized commercial job.
Architect---------Well connected, high dollar.
Designer----------Well known, expensive
Manufacturer-----Multi-billion dollar corporation.
Retailer-----------Million dollar a year company.
Installer----------One or two guys who may break 100K
GC---------------Multimillion dollar a year company
End User---------Multi Million $ company.
If there is any problem, who do you think among these seven entities can not afford to defend themselves? Who stands at the bottom of the pile?
Yet who is asked to go against Best Business Practices most often?
NOTHING will ever change until the manufactures REQUIRE that their products be installed with at least minimum standards. Until that happens (a cold day in ?) there are NO consequences for the players to meet standards. So everyone pushes until the little guy (installer) gives in and does the job "on a wing and a prayer."
Just a guess, but I'll wager that everyone here and most installers have taken a "bath" by doing things like this at one time or another. I admit that my education was to the tune of 15K, David Hunt admits that he was educated by the IRS, I know several others here were educated in one way or another. The important this though is that we learn! Don't continue making the same mistakes.