There are probably some good reasons for economics and commercial use, but I don't quite see why someone like me should choose an LM7805.
At $3-4 for the cheapest "spec'ed" DC/DC converter, they're about 10x more expensive than a linear regulator, and would become the most expensive component on the board.
(The 10x multiplier stays about the same for Aliexpress parts, though now you're talking $0.60 vs $0.06.)
7805s, of course, you can buy nearly anywhere...
With the ubiquity of 5V USB power supplies, I'm about ready to throw away the "DC-IN/regulator" section of most arduino designs entirely, perhaps even having a separate "power only" USB jack.
I did design a 4809-based board that uses aliexpress modules for power and usb components. I haven't gotten around to actually populating a board with the power modules, though. Having to set that pot to get correct voltages is a little nerve-wracking.
