It was important for Vito to be seen in public meeting with Fanucci--and for Fanucci to be seen leaving Vito, amicably and alive. That way, Vito had an alibi, as long as nobody saw him climbing over roofs to intercept Fanucci outside his apartment door.
In the novel, Vito has Fanucci call on him in Vito's apartment to get the money. Vito's wife and the other women in the building were sitting on the stoop, conversing. They saw Fanucci leave the building alive, and could vouch for that fact if Vito'd been arrested. Meanwhile, he was climbing over roofs to intercept Fanucci.
Good points and being that Vito met and paid something. Fanucci would not be inclined to tell anyone close to him to "watch out for this Vito character" he doesnt want to pay and there might be trouble.
