An internal application that three departments open every morning. An API a customer integrates against and notices the moment it changes. A job that runs overnight and has to be finished before anyone logs in. That is the kind of code we are comfortable in, and it is a different job from writing something new on an empty screen.
The range is wider than it sounds. We have built large C# systems for corporations, with all of the process and paperwork that comes with them, and we have built small websites for small companies where the whole thing started as one person's idea. Both get the same attention.
We are also not particular about whose code it is. A good deal of what we maintain we did not write, and some of it we would not have written that way. That stops mattering once it is in production and people are relying on it.