Manchester United started their top flight campaign with a 4-0 thrashing of West Ham at Old Trafford.
New man Lukaku was on target twice and Mourinho thinks it is important for players at new clubs to net early for their confidence.
But the Special One does not believe being top of the table after the first game of the season is anything significant.
He said: "It is important for new players in new clubs, everybody expects goals from the striker.
"It is nice for Morata, Rooney, Lukaku, Lacazette to score. It is nice for their confidence.
"The fact we start winning and are top, it means nothing. The performance and the levels of confidence is what means a lot to me.
"We lost two points aaginst them last season and had similar games where we were dominated. Today we got the three points.
"The reality is that in the last part of the game, instead of being boring and controlling the game, we scored a third goal and we could enjoy it."
United return to action next Saturday in the Premier League when they travel to Swansea.
West Ham will look to bounce back at Southampton.
