Maybe because is not stable enough and having stability is the most important thing for a player while Lukaku doesn't have this. Also, Lukaku is not a cheap player and Inter Milan should spend too much for it while he is getting old, and currently, he is 30y old and not young anymore.
Although he couldn't play very stable, his performance was quite good toward the end of last season. I think it is not a bad idea to sign him, he still contribute well for Inter Milan. Regarding the price, €40m isn't too much money for a quality striker like him. It is true that he is no longer young, but he still can perform well and has no problem with his fitness. I think he can play until 35 years old, so there are still 5 years for his career.
I heard other news that AC Milan is also interested in Lukaku. So it's going to be really interesting. But it seems that Lukaku personally is more comfortable playing at Inter Milan. I think Inter Milan should be bolder to buy Lukaku from Chelsea. Because AC Milan might suddenly appear and intend to buy Lukaku.
Yep. Lukaku clearly prefer to choose Inter Milan. However, if Inter Milan no longer has the intention to sign him, Lukaku should look for another club. AC Milan is a strong club, too. It should be a great place for him, moreover Giroud is already 36 years old and his contract is almost over in AC Milan. If Giroud doesn't extend his contract, Lukaku can have a chance to be the main striker in AC Milan.