exiftool doesn't remove meta data of MP4 (stuff like "Promotion URL" and "Author URL") I have a MP4 file with ad URI in meta data. I wish to remove those:

exiftool example.mp4
ExifTool Version Number         : 10.40
File Name                       : example.mp4
Directory                       : .
File Size                       : 12 MB
File Modification Date/Time     : 2017:03:19 06:53:08+01:00
File Access Date/Time           : 2017:03:19 06:53:08+01:00
File Inode Change Date/Time     : 2017:03:19 06:53:08+01:00
File Permissions                : rw-r--r--
File Type                       : MP4
File Type Extension             : mp4
MIME Type                       : video/mp4
Major Brand                     : MP4  Base Media v1 [IS0 14496-12:2003]
Minor Version                   : 0.2.0
Compatible Brands               : isom, iso2, avc1, mp41
Movie Data Size                 : 12077146
Movie Data Offset               : 11050
Movie Header Version            : 0
Create Date                     : 0000:00:00 00:00:00
Modify Date                     : 0000:00:00 00:00:00
Time Scale                      : 1000
Duration                        : 0:00:30
Preferred Rate                  : 1
Preferred Volume                : 100.00%
Preview Time                    : 0 s
Preview Duration                : 0 s
Poster Time                     : 0 s
Selection Time                  : 0 s
Selection Duration              : 0 s
Current Time                    : 0 s
Next Track ID                   : 3
Track Header Version            : 0
Track Create Date               : 0000:00:00 00:00:00
Track Modify Date               : 2016:12:09 04:26:57
Track ID                        : 1
Track Duration                  : 0:00:30
Track Layer                     : 0
Track Volume                    : 0.00%
Image Width                     : 360
Image Height                    : 640
Graphics Mode                   : srcCopy
Op Color                        : 0 0 0
Compressor ID                   : avc1
Source Image Width              : 360
Source Image Height             : 640
X Resolution                    : 72
Y Resolution                    : 72
Bit Depth                       : 24
Video Frame Rate                : 29.97
Matrix Structure                : 1 0 0 0 1 0 0 0 1
Media Header Version            : 0
Media Create Date               : 0000:00:00 00:00:00
Media Modify Date               : 0000:00:00 00:00:00
Media Time Scale                : 44100
Media Duration                  : 0:00:30
Media Language Code             : und
Handler Type                    : Audio Track
Handler Description             : SoundHandler
Balance                         : 0
Audio Format                    : mp4a
Audio Channels                  : 2
Audio Bits Per Sample           : 16
Audio Sample Rate               : 44100
Subtitle                        : example.com
Promotion URL                   : example.com
Author URL                      : example.com
Category                        : example.com
Avg Bitrate                     : 3.17 Mbps
Image Size                      : 360x640
Megapixels                      : 0.230
Rotation                        : 0


I tried 

exiftool -all= example.mp4
    1 image files updated


But it didn't work, the URI still in MP4.
Exiftool is great at removing metadata from photos and viewing metadata from others. ffmpeg is must better to use to remove metadata from videos.  A generic "remove all" command would be this. [credit to a guy who once wrote  this on a forum. You sir, are amazing.]

ffmpeg -i in.mov -map_metadata -1 -c:v copy -c:a copy out.mov