For a long period, answers with 'reasoning' were indeed not moderated on IPS for 'lack of back up'. Also, from basically the first days of the site people have noted problems with posts with no explanations (like one line answers) and wrong explanations (e.g. cultural differences). Even our earliest question on implementing a back-up policy already mentions what back up is supposed to be:
The folks at Moms4mom owned up to the subjective issue and came up with a set of principles to create useful subjective discussions on parenting: the Back It Up! Principle. Back It Up! means that your answers must be based on either:
- Something that happened to you personally
- Something you can back up with a reference
This is a quote from the Good Subjective, Bad Subjective blog post. That same blog post talks a bit more about the value of experience. I'm particularly fond of this quote:
Sharing an experience takes at least one paragraph; ideally several paragraphs. If I’m asking about how to bake cookies, don’t give me a list of grocery items: milk. butter. vanilla. eggs. There is virtually nothing I can learn from a short, static list of grocery items that make up a recipe. Instead, tell me what happened the last time you made cookies from that recipe! Share your detailed experiences, so that we all might learn from them.
Here, we also start touching the point why just reasoning (however strong it may appear) just doesn't cut it on IPS. Presume I told people that I would bake cookies for them, using a chocolate chip cookie recipe. But I don't have chocolate chips and need a replacement.
An answerer can reason that raisins are going to be a tasty replacement for chocolate chips in a cookie recipe, and add a strong argument that they're both sweet, look similar, and don't require any other changes to the recipe. But if they never did use raisins instead of chocolate, shared those raisin cookies and saw people's disappointment at eating a raisin cookie where they expected a chocolate chip one... the whole strong reasoning just became 'wrong'. And IPS just turned into a site where voters and commenters can fight over raisins vs. chocolate chips.
Why is a strong explanation of the logic behind your answer not considered to fulfil "backup?"
Well, as mentioned above: explanations of the logic behind an answer are still pretty subjective. They can be argued with, over, and discussed at length. As I said at the beginning of this post, there was a long period at the beginning of IPS where such answers weren't flagged and deleted for lack of back-up, and there were A LOT of arguments in comments.
It is much harder to argue over personal experience (you just write down your own personal experience in another answer, or point out in a comment that something once didn't really work out for you because Y, so the original answerer can improve on their post). In the same way, it's much harder to argue with sources.
Either way, to point out a flaw, people need to bring either their own experience or better sources, not just their thoughts and reasonings. Having a firm back up policy helps to prevent IPS from "falling into the predictable destructive patterns of random discussion, debate, and opinion that turn a site from a learning experience into a glorified cheap-thrills gossip rag." (quoted from Good Subjective, Bad Subjective).
Problems caused by the 'strong explanation' approach led to IPS becoming more strict, and from this question onwards we decided that we really need those sources and experience. The accepted answer summarizes it well too:
As long as people are allowed to post confidently clueless answers, they will do so. And as long as those answers are present, the sufficiently convincing ones will gather upvotes - there will be other people who have similar gaps in experience or knowledge.
Look at it this way: The strongest explanation you can possibly give an answer on a subjective site is by using personal experience, or references. Anything else will just be an uninformed opinion.
On a side note: Em already linked you to this question from shortly after we initially started yet another attempt at really enforcing back up as just being experience or references. That post didn't completely undo the entire enforcing of the policy, but the more strict version of the policy (experience or sources) really got momentum after IPS was taken out of HNQ.
We suddenly had a moderate-able amount of answers, and voting on back up policy posts wasn't skewed as much by HNQ visitors and potential loss of reputation gains, so it became a bit clearer that this was what a big core part of the site had been wanting all along. I'd like to think the posting of the Citation Expectations, that we copied from RPG meta, as the 'formal' starting point of enforcing the strict backup policy.