This is the first time I've heard of them, but thanks for giving me something else to learn about. Wikipedia (
Air start system - Wikipedia, the free encyclopedia ) explains the air start system as being used to start large engines at a time when batteries weren't as reliable as they are now. So, the answer as to why they aren't used is the battery technology has improved for companies to think that the battery/glow plug combination is more reliable.
As to whether there's a company that still makes them, amairstarters.com is out of Houston and has charts to match engine model numbers with models of their starters.