What Witcher books did you guys read? Because I am re-reading the saga right now, The Tower of the Swallow to be exact, and Geralt is travelling and going through adventures with 4 other people for the whole book so far(Cahir, Regis, Milva and Dandelion), a companioship as they call it themselves. And Angouleme joined them, so that makes it 5 companions. It's been like this, in different configurations, for quite some time already(I mean, in the books). So no, Geralt of Rivia doesn't always work alone. Quite the opposite.
And yet, CDPR decided to have Geralt as a sole main character, without any regular party or companions. Small exceptions have been made in the Witcher 2 when you can control other characters or in the quest with Brigida Papebrock, but that's about it. So maybe CDPR prefer to concentrate on the main protagonist and his own, personal story, with many awesomely written NPCs he meets throughout his journey, rather than splitting their efforts on additional development needed to bring to life a fully controllable companions.
And so far, from what CDPR mentioned in the interviews, CP2077 will also concentrate on the protagonists personal story.
But as Sard pointed out, this is off topic here.