In its simplest terms, it is a bit careless for a web application developer to allow those kinds of errors to be seen by actual application users. The information that is contained on the screen of death only belongs to the application developer, not a visitor to your application. For a determined hacker, this information will give them somewhere to start as it gives out internal information on the application that may give a lead and an insight into how your application actually works.

Error handling needs to follow a proper thought process. This applies even in seemingly trivial situations where an application developer needs to use safe casting and proper type conversions such as TryParse, as this goes a long way in preventing ad hoc errors that can result in a screen of death.