What's the oldest system you work with? In any technology-led business, there's at least one chunk of hardware or code that barely anyone understands. It's why people who know COBOL can command high salaries maintaining critical systems that have built up a gnarled shell of interoperability frameworks over the years. It's why people maintain ancient server versions, just to support that one vital piece of software that won't work on anything more recent.
It's the same virtually everywhere – time spent on maintenance or improvement of existing features is time that can't be spent on that vital feature that the business or customers need. So that hack that makes it work just for the project, the one that absolutely will be replaced as soon as everything's up and running makes it into the final build, and from there into "I can't believe anyone would choose to do that" legend.
I'm quite lucky in that I work for a company that has relatively little obstructive cruft lurking around the backend – in fact the oldest code I work with is ASP.NET 2, on the SSC forums (supporting IE6 notwithstanding). But even if you keep up to date, it's hard to keep that maintenance burden low. Automation can help, but it has to be widely-understood so that it can be maintained or altered when the original author moves elsewhere.
DBAs might have it easy comapared to some software disciplines though - I like to ponder the issues future code archaeologists are going to have with ever-changing web frameworks they encounter when the time comes to update them. Maybe there'll be some equivalent of the Wayback Machine that captures freeze-frames of trendy web development environments at a given point in time?
What business-critical logic is stored in Access on an old laptop in a cupboard somewhere? And what do you do to make sure you've got time to make improvements to your systems?