I think we all have this vision in our minds that the ammo factories have have one dedicated machine for each caliber, and that machine runs 24/7 making ammo as fast as possible. That picture is not quite true.
While it's true they might have 3 or 4 machines running 9mm Luger all the time, the production of other calibers is not that way. Say for instance, Remington sold 15 million 45ACP last year. This year they might look at the 2019 sales of their own 1911 guns in 45 and see that sales are slightly down. Based on that, they may elect to only run 14 million rounds of 45ACP this year. When that quota is complete, then that same machine is re-configured to run 380Auto or 38Super, or some other low-sales cartridge. It might not be reconfigured for 45ACP again for another 11 months. Your personal reloading would be done the same way if your reloading machine took 10 days to do a caliber change. Stopping everything to run a box of 50 for a pal simply wouldn't be in the picture at all.
While I'm sure the factories are saying, "Gosh, we could have sold 20 million 45ACP if we had it". They had a plan at the first of the year, and it didn't include a global pandemic, or Democrat operatives turned loose on city centers to burn and loot. So the factories are running on their plan. The plan is certainly modified by now, but the supply stream is so long that some calibers won't be back in stock for months.
If your response to this story is along the lines of "Well, that's just stupid" then allow me to point out that if you're now out of ammo, then your plan wasn't much better !!!!
And furthermore, if you're one of the people who 10 months ago was saying, "I'm not going to reload because you can buy XXX caliber cheaper", well how's that plan working for you today, my friend ??
This happened 3 or 4 times before, and guess what? It will happen again.