Why are there two different close reasons for questions that aren't about the site's topic?

Question

On both Meta Stack Exchange and Super User, I noticed that there are two close reasons to choose between when a question isn't about the topic of the site (Stack Exchange on Meta and computers on Super User). There is a "blatantly off-topic" reason and a "not about X within the scope defined in the help center" reason. These are the two close reasons on Meta Stack Exchange for questions that aren't about Stack Exchange:

This question does not appear to be about the software that powers the Stack Exchange network, within the scope defined in the help center.

Blatantly off-topic (this question has nothing to do with the software that powers the Stack Exchange network)

And these are the close reasons on Super User for questions that aren't about computers:

This question is not about computer hardware or software, within the scope defined in the help center.

Blatantly off-topic (this question has nothing to do with computer software or computer hardware)

According to this answer, the "blatantly off-topic" reason is replaced with an "other" reason when the user gets the privilege to vote to close. But since there is already another close reason for questions that have nothing to do with the site's topic, I'm not sure it's really necessary to add a "blatantly off-topic" reason. I would find it more logical to simply remove that reason for users who don't have the privilege to vote to close.

I just flagged a question on Meta Stack Exchange about hair dryers as off-topic, and I was confused that there were two almost identical close reasons that worked for that question (and for any other question that is not about Stack Exchange). On Stack Overflow, where there is no "not about programming within the scope defined in the help center" reason (the reason for that is explained here), "blatantly off-topic" is useful for <3k users so that they can flag questions that are not about programming, but I don't see the use of it on sites like Meta Stack Exchange or Super User that already have a close reason for such questions.

I guess that on Super User, there is a small difference between the two close reasons, since programming questions would fit the first close reason but not necessarily the second one, but I still don't see the need to have two very similar close reasons. And on Meta Stack Exchange, there is almost no difference between the two reasons, either a question is not about Stack Exchange and is off-topic, or it is about Stack Exchange and is either on topic or fits in a different close reason (for example questions about a specific site).

My question is why have a "blatantly off-topic" close reason on sites which already have a "not about X within the scope defined in the help center" reason? Why not just remove the "blatantly off-topic" close reason on such sites for users who have less than 3k reputation? Wouldn't it be less confusing if there was only one close reason for questions that don't have anything to do with the site's topic?

Answer 1

♦ moderators have the option to create up to three custom off-topic close reasons^*. One of them might or might not be a general 'not in scope' close reason.

On the other hand, the "blatantly off-topic" close reason is a system-generated one. Because of the flexibility, the system cannot 'detect' if a general 'not in scope' reason is present. Note that the wording differs between sites, and the close reason on Meta Stack Exchange doesn't even link to the /help/on-topic page, so the system couldn't even check for that specific link.

In the end, it doesn't really matter which of the two you choose. I agree it's a bit confusing, but you are a duck, not a donkey.

_{^* some sites, like Stack Overflow and Meta Stack Exchange, have more, but that's an exception; some sites have less if they don't need that many custom reasons.}