Everything decays. The hardware that your software runs on dies and no one can find a replacement. The regulations covering your business change. Your vendor st

Everything decays. The hardware that your software runs on dies and no one can find a replacement. The regulations covering your business change. Your vendor stops supporting SSLv2Hello. Your clients ask for a feature that your competitors provide. IBM raises prices on your contract that renewed last week to make up for flagging revenue. Suddenly 3-9s of uptime isn't enough for your clients and you need a second datacenter. Once it starts costing more than $200 a person/hour to deal with things like this you are kinda hosed. Especially when it will take thousands of hours to make a change. Hence why everyone wants to move to cheaper languages like Java, Node.JS, etc... Otherwise, you end up with a COBOL system running on a linux virtual machine that is emulating an IBM mainframe from 1992 that is nearly impossible to maintain because the developers have all died or retired and left no documentation. Your remaining contractors have billed a quarter million in costs and the change still isn't working.