All motown acts were subjected to "charm school" to:

All motown acts were subjected to "charm school" to help singers develop proper etiquette of performing on stage, presenting themselves in front of the public and how to talk to the media.

Many of these singers came from poor backgrounds and had a rough upbringing.  For example, the Jackson 5 did not know much about city life, business or popular music in general.

They had to be  taught the 'social graces' which many of their audiences expected from them and loved them for.
There were certain things they had to wear, certain things they could not say and certain mannerism they had to adopt to project a popular and likeable image.