I can only guess, Bhaveshn, that you are familiar with Solidworks and are trying to accomplish a similar task with dimensions imported from the model file.
SE isn't SW, thankfully. SE does not drive the model through the draft file and therefore even imported dimensions are still "reference" dimensions. There is no benefit, short of saving a little time, to import the dimensions or create them directly in the draft.
Conversely, in SW, imported dimensions can change the model whereas "drawn" dimensions can't so it behooves the SW user to import the dimensions and move them to the appropriate view on the draft file if you plan on adjusting the model through the draft file. Again, not the case with SE.
Its not about always retriving dimensions from model. Assume a case, when dimensioning a detail view. If you want to pick a origin which is out of view boundary. The best way may be first give dimension in parent view and move it to detail view, isn't it?
There may be other good uses apart from it, just need to discover.
The trick to do that in SE is to modify the detail view boundary so it includes the out of view geometry.
Place the dimension.
Modify the dimension to hide unwanted extension lines.
Then modify the detail view boundary again back to its original smaller size.
