I sometimes think 3L5W is occasionally necessary, such as multiple repeat problems, problems which appear to require an unusual level of stupidity or incompetence, and problems where the risks are really, really high. In about a year and a half, I have not asked for one yet, although a couple of suppliers came close. I often ask for 5 whys on the problem and a 5 whys for the escape.
Where I work, we usually just formally notify the supplier of problems and expect them to fix, without issuing a SCAR. SCARs are reserved for big, serious, or repeat problems. As a result, I usually ask in a SCAR for 5 whys about the problem and 5 whys about the escape.
In the industry I work in, 100% and large sample inspections are common, so an escape frequently is due to flaws in the inspection methods rather than parts not being in the sample inspected. And on the next order after a problem, I expect you to be looking closely for the problem, so any escape leads me to question the inspection.