I think that those question regardless of how well they were received are good questions to have answers too. The problem with some of these questions is that they require a lot of work. Frosted glass is an easy one but others, e.g. asphalt or procedural marble would require some R&D.
Most cases OP will not have made an attempt to create the material themselves, which is why it takes a lot of effort to answer these questions. So that there question is indeed a request.
I think we should allow all material questions to stay under the following conditions:
complex shader questions need to show work, this is not a request site
simple shader questions like frosted glass do not need to show work