I get the feeling he is very competitve, so seeing Salah banging in the goals, he wants to score as well, so sometimes he takes a shot on and is selfish when he should pass, but when you see some of his finishes, like against City, you can see why he does it.
Also, if we and his team mates don't know what he will do, our opponents can't predict him either, so even when he's not on form, our oppnents have to mark him so he occupies defences making space for the likes of Salah.