Why did Don LaFontaine replace Bill Conrad as Narrator?

Originally William Conrad did the narration for The Making Of Star Wars which aired on CBS back in 1977. When this was released on VHS by Lucasfilm in 1995, the audio was completely redone. Anthony Daniels came back & re-recorded his dialogue & Bill Conrad was replaced by Don LaFontaine. Some of it was completely rescripted. I originally thought perhaps it had something to do with copyrights owned by Conrad's estate. However, when this was released again on Blu-ray in 2011, Lucasfilm included the original "Conrad version" in the archival section of bonus disc 3. What the heck??? Anybody know why the "Lafontaine version" was created in the first place?