Lure modifications are usually done for these reasons:
1. change in action
2 change in shape/ profile
3. change lure size - length and/or diameter
All three affect each other. Modifications can make a difference - or at least seem to when fish bite the modified lure as well as the original.
Dipping the body of a soft plastic lure increases its profile and size (diameter and length). The tail was already wide, so the mod matched the body to it. All homemade lures must be tested and this one was no different to establish the future need for dipping in a Pyrex cup of hot liquid plastic. It did great any time it was fished.
Examples: