As I have said before, you don't see an arranger on a 'Pro stage venue', because IT IS NOT NEEDED ... For most players, the purpose of an arranger is to augment the sound of an INDIVIDUAL player, so that it sounds like there is more than one person playing ... on MOST 'Pro stage venues' there is a bass player, guitar player, drummer, horns, etc. etc. or any combination of those instruments, which are provided by the arranger
To take it a step further, in many 'Pro stage venues', the keyboard player has several different kbs/synths to use, utilizing the best that each has to offer ...