Staying fresh has its own costs, and those would have to be made absolutely clear and transparent and clients must pay them. That's actually very difficult to do politically, especially when you have lowest-price bidding schemes.

Code is legacy the moment it's put into production. Keeping technical debt from piling up, and keeping on the bleeding edge to avoid costly maintenance of old systems is extremely expensive. And the costs escalate very quickly when you're talking about airplanes. The cost of dealing with legacy becomes acceptable very quickly.