Having spent half a lifetime in the industry (more years installing and servicing alarms than you've been alive judging from your vernacular), I have significantly more knowledge of what most installers do than you, my friend.
Nope. It was a specific and accurate statement of the condition of the industry. Once you've been around long enough to know something about it, please come back and share with us. For now it's best you sit on the sidelines and lurk.
Better than you, probably, but my statement wasn't an analogy.
Most DIYers don't need to do line loss calculations because most DIY installations are medium to large residential jobs which rarely exceed the capacity of standard 22/4 cable. However, a fair number of my DIY clients also install commercial fire alarm systems which require such considerations along with stand-by battery calculations, etc.
Also, several of my DIY clients who routinely post in a certain other newsgroup are electrical engineers, etc. Most of them could teach you (well ok, maybe not you but others with the capacity for thought) how to install advanced home automation systems.