Because he's shite.
That's the long and the short of it.

Same reason why Liverpool are not in the Champions League init....................Not good enough.

He's too busy writting prequels to Star Wars.

The only reason is he has Rafa disease which destroys talent of a brazilian footballer

it's because the brazil manager has to select his teamed based on how well he has seen them playing for their own team but Lucas always plays good for Liverpool when rafa plays him in the position he usually plays when he is playing nationally he scores goals and plays good but then rafa changes him back again or doesn't play him in the next match so because lucas hasn't been playing well as he is not in his best position that might have been the reason why