This is true, but most programmers don't and won't ever get a deep understanding of crypto. For that large majority, it makes complete sense to ask "What do th

This is true, but most programmers don't and won't ever get a deep understanding of crypto. For that large majority, it makes complete sense to ask "What do the people who do understand crypto use in a case like this?" and use that. That kind of copying is clearly inferior to either gaining the knowledge to make an informed decision or hiring an expert to do it for you, but for most projects that need crypto neither one of those is practical. So, copying the experts is the best practical approach in most cases.