After a short investigation I figured out that the application you mentioned in your post - DXF View - is not able to show 3D Solid objects in DWG / DXF files.
So if your drawings contain only such kind of data, and the person you are sending your DWG / DXF files is using "DXF View" application to open your files, than he/she will not be able to see the contents of the drawings.

Maxim