Lukaku played for Wba and Everton and scored 20+ goals in the league in what, 3-4 seasons?
Morata is not proven in the league. He's not proven as a consistent starting 9. He's not proven to contribute consistent goal tallies for lesser teams.
Lukaku on the hand, is proven on all three fronts, making him a much lesser risk than Morata. Whilst there is unanimous agreement that Morata will probably be a great number 9, the large fee makes us favour someone more established. Lukaku is certainly more established than Morata. No one can really deny that.