There still are developers building and extending applications using languages like COBOL, since banks and other such organizations rely on ancient systems to power their day to day businesses. Some of these systems are mission critical, so instead of building up new ones, that might fail or have bugs, they prefer to continue using these ancient systems.
It would seem, that even though upgrading to newer software can be a pain, and a risk, there are tools and methodologies out there to make this transition safe. The benefits of upgrading to newer systems would of course be considerable - ease of maintenance, ease of finding skilled developers etc.
I have not yet heard of companies that are aimed at providing this service. Do they exist?