Yeah I thought you were asking if such a feature exists but re-reading your post I can see you weren't, my bad.
Still it's a useful tip for anyone who might not be aware.
This!!! If I needed/wanted just about any SG blend at this moment, I could have it in my hands inside of 2 weeks with minimal effort. Would it be nice if it was on the shelf in unlimited quantities at every B&M and Internet Retailer you turn to? Absolutely. And while that's not the case, it is readily available if one is willing to put a little effort in. In addition to the above, you can look at Synjeco where you can also get the SG Plugs.
As others have said it’s because they are good and they don’t produce a ton. If I could find SG Lakeland Dark for good internet prices. Around $11-12 I’d buy 20 of them.