Many IT professionals believe if it isn’t broken don't fix it. A recent survey found that 50% to 60% of core processes in some verticals still run on mainframe systems using legacy, often poorly maintained software. After all, it still works.
Resistance to modernization does not come only from an “if it isn’t broken” attitude. Change brings risk, so it might appear prudent to delay major infrastructure changes. Also, many large organizations have sizeable investments in mainframes loaded with years of accumulated data and that data may have been incorporated into monolithic mainframe software applications.