Because it makes zero sense when you tie in the FI prophecy, Im, and God Valley stuff.
Also...going to Elbaf after Laugh Tale?
It's not luffy who will destroy FI, it's lurking legend, who will then target zunisha and take it to elbaf
After wano, we are gonna have three simultaneous mini arcs, which are Mary Geoise, impel down and vegapunk island (one island for each of monster trio)
During these which should last around 30 to 40 chapters, we will have introduction of lurking legend, imu, gorosei, bb destroy Mary geoise, kizaru Magellan and lucci defeated, rescuing Hancock, and basically tying all loose ends (vegapunk, ancient weapons, some lore ... etc)
After lurking legend destroys fishmen island and targets elbaf next, monster trio will reunite in New marineford (after escaping their three islands), where they escape three admirals (brief clash) and set course to Elbaf (where rest of SHs were already at and usopp already had his alone time and sub arc with giants, convincing them to prepare for war)
So by the time we have 90-100 chapters left, it will be shown that luffy and his allies are headed to Elbaf, lurking legend too, bb pirates, red hair pirates, imu and his small team (not revealed yet), akainu decides it's time to end everything and also takes entire army, Dragon and revos go too and much more
It's basically similar to arabasta arc but instead of "they all clash at alubarna" it will be "at elbaf" instead
And yes, laugh tale will be visited right before elbaf
The plan has always been:
WCI ---> Wano ---> Crew Separated ---> Laugh Tale ---> Elbaf ---> Ending (True treasure that Roger couldn't get)