People using Dichlor-then-bleach in their spas (too keep CYA in check) and that use sufficient chlorine to always measure FC before their next soak also have not needed to shock and that has been rather high bather load. You are right that most people don't use enough chlorine -- especially in spas. Roughly speaking, it takes around 3-1/2 teaspoons of Dichlor or 5 fluid ounces of 6% unscented bleach or 7 teaspoons of MPS to oxidize the bather waste from one person-hour of soaking at high temps (100F-104F).
Yes, you need to use a sufficiently high FC/CYA ratio to prevent algae growth and a sufficiently high FC to accommodate the bather load. It is true that shocking will cover up the sins of poor pool maintenance (to some degree), but I'd rather teach people what to do properly. It's similar to using an algaecide. You have to use one if you don't watch your CYA level, but if you manage your pool properly you don't need to use it at all.
As for above-ground pools, including Intex pools with small filters, they still need to maintain the chlorine levels properly and I totally agree with you that anyone not doing that is going to run into trouble and that shocking helps to "make up" for too low chlorine during the week. There have been many Intex pool users at The PoolForum
and Trouble Free Pool
who have managed their water without weekly shocking and without getting algae or other issues.
There are, of course, very legitimate times when one should shock including fecal accidents, dead animals, vomit, or lots of other organics including pollen that get into a pool or any other time one notices the overnight chlorine loss > 1 ppm or a significant CC > 0.5 ppm. The best way to deal with pollen and other organics that tend to consume a lot of chlorine is to get a skimmer sock as they will collect a lot that you can then regularly remove rather than get caught in the filter and consume more chlorine (until the filter is cleaned).
So we're not disagreeing technically. You're just wanting to give safer advice assuming people won't be responsible and I'd rather give advice for those who can be responsible and caveat it saying that if you aren't, then there are fallback activities such as weekly shocking that can be done.