Lightroom :: How To Avoid Changing Original JPEGs

I'm using Lightroom 4.1.
 
There an option in Catalog settings called "Automatically write changes into XMP". I like it. Very much. But not for JPEG.
 
The reason is rewriting the original datetime of JPEG file by Lightroom. It rewrites it even if I don't make any changes in the Develop module. For example, if I simply change item's Caption in Library or item's Copyright field then Lightroom instantly changes my JPEG. I don't want such behavior. I'll try to explain why.
 
Sometimes datetime of the file can contain important information about when this photo or video was made. For example, some phones don't write EXIF information into the video files (e.g. 3gp). Therefore, the only place where we can see when this video was shot is the datetime of the file. If Lightroom rewrites original datetime, we will lost this info.