A funny way of asking.
I guess the easy answer is:
If you can satisfy all your data analysis requirements without scripted calculation views, then consider yourself lucky.
There are many scenarios that the graphical environment cannot support efficiently and scripted calc views allow to tackle those.
Also, depending on your development knowledge, writing SQL statements may feel more natural and productive than connecting boxes.
In case you're actually looking for a one-two-three-step-guide when to use what, you won't get lucky.
The different view types are tools like any other set of tools. Function does overlap and it's up to the developers discretion to consider and decide which will do the job best for any given situation.
- Lars