This question has been marked as a duplicate of: Can we encourage people to put more research into questions?
While the linked question is about making people actually think and read up on the topic they ask about, this discussion is about finding ways to make people use site-tools and check out the automagically proposed questions when they write up their own questions!
Recently whenever I browse questions I see at least one if not more that could be answered or at least improved by going through answers to previous questions we've had on the site.
E.g. this question about mammals with blue blood. Reading the question I immediately had two thoughts:
a) Have you actually googled this? Tried to read up on the topic?
b) You have found this stack, have you tried looking if the question has already been asked?
I know at least the answer to the latter must be no, because I know this question has come up already, and I know this question has been answered amazingly well here (and not only about blue blood).
What I also know is that searching is hard. Terms & words that I use when thinking about a question might not necessarily match those used by others. When searching I have to look up existing tags, and synonyms of words I would use - I have to be ready to do that extra effort. But I know that the effort is worth it, because it helps me with whatever I do or try to do eventually.
Searching the meta for the topic I find exactly two questions/discussion on the subject over the last 4 years:
How can we incentivise people to use tools like the site-search or related questions before and while asking questions?