Not really, because the risk of such a fine is ridiculously low. From reading up on the incident, it seems like it was more a matter of a software update rather

Not really, because the risk of such a fine is ridiculously low. From reading up on the incident, it seems like it was more a matter of a software update rather than specifically the use of legacy code that caused the incident. UBS was fined because the outages were unacceptable to consumers and regulators and because "the potential for problems had been raised in an internal audit two years before the incident took place in 2012"[0] and nothing was done. One could argue that legacy code makes that more likely because of unseen factors that predate the people actively working on it. It's hard to miss a landmine, after all, if you don't have any clue that it's there. But while a rewrite might eliminate that specific risk, it does so by inviting a lot of new ones to replace it. In some ways, the risks are probably greater as you need to figure out possibly decades of business logic and then re-implement everything. From a business decision perspective, the existence of legacy code on its own is an insufficient argument on its own. After all, the problems inherent in legacy code will eventually surface yet again in another 10-15 years anyhow. The better solution in most cases would be to identify specific problems and determine what can be done to hedge against them. 0. https://www.theguardian.com/business/2014/nov/20/royal-bank-of-scotland-it-breakdown-56m-pounds-fine https://www.theguardian.com/business/2014/nov/20/royal-bank-...