Whenever you move data between programs or save files in formats other than an application's native format, a process of translation occurs. And, as in the translation of text from one language to another, the translated version will differ from the original. Objects will shift on the page. Sending pictures electronically over the Internet by other methods such as electronic mail. Creating graphics for on-line publications.
Disk space is a factor.
Adobe TIFF Creating images for print publications. Transferring vector artwork between software packages. When you need to insert the graphic into a macintosh version of Microsoft Word, WordPerfect, or other word processor. When you need to insert the graphic into a macintosh version of PowerPoint. When disk space is of no concern or your graphics are very small.