Why does robin gibb never played instruments on the stage and his name not mentioned credits which he always only vocals?

Robin Gibb did play instruments on stage and was credited for his contributions.

Here are some examples:

* In the early days of the Bee Gees, Robin played rhythm guitar and sang backing vocals.

* He also played drums and keyboards on some of the Bee Gees' later albums.

* In live performances, Robin sometimes played acoustic guitar or keyboards.

Robin Gibb was always credited for his contributions to the Bee Gees' music. His name is listed on the credits of all of the Bee Gees' albums, and he was also credited as a songwriter on many of their songs.