I Think,,,
it's because they on-line gun stores rarely have stock,,,
They all get from the same firearm distributors,,,
Then they order it in and send it to you.
They announce availability when the distributor has it in stock.
At least thats what my gun store guy told me,,,
I noticed because I asked him to order me a pistol,,,
When he couldn't get one I hit my 2nd, 3rd, and 4th string dealer.
No one could get me one,,,
Two months later I got phone calls from them,,,
All within a week of each other saying they could get one now.
Who knows,,,
Maybe true, maybe not,,,
I just repeat the info told to me.