Because all together is a phrase, as separated is a word. You can say altogether though, but that's an adverb, so not entirely the same thing. Separately is from the Latin, 'spartus', which is 1 word. All together means the total amount or number in a single mass. It doesn't need to be joined
The cast of O Abajour - 2011 includes: Amanda Alves as Carol Spartus Alves as Luizinho Chapa-quente Adriana Bandeira as Laura Daniel Bouzas as Murilo Daniel Braga as Moby Oscar Calixto as Cardoso Higor Campagnaro Rod Carvalho as Alcir Verena Isaack as Amiga Manu Alexey Koba Camila Lorenzo as Gabriela Luca Machado as Dr. Fernando Alexandre Machafer as Rick Etiene Mascarenhas as Manu Rodrigo Molina as Lobo-Mau Alex Reis as Guilherme Robson Rocha as Canivete Remo Rocha as Gustavo Marcella Strufaldi as Bruninha Enzo Valentim as Enzo Pietro Valentim as Pietro