I think this is and will continue to be a common use case. I'm very thankful for these applications that the data was still stuck in a crusty old relational database for me to work on top of as I built a new application.
It's going to be interesting when this same problem occurs years from now when people are trying to reverse schemas from NoSQL databases or if they become difficult to extract.
The only sticking point is when business logic is put into stored procedures. On one hand if you're building an app on top of it, there's a temptation to extract and optimize that logic in your new back-end. On the other hand, it is kind of nice to even have it at all should the legacy app go poof.
It's going to be interesting when this same problem occurs years from now when people are trying to reverse schemas from NoSQL databases or if they become difficult to extract.
The only sticking point is when business logic is put into stored procedures. On one hand if you're building an app on top of it, there's a temptation to extract and optimize that logic in your new back-end. On the other hand, it is kind of nice to even have it at all should the legacy app go poof.