#3 Vince McMahon will offer Ambrose something better

Even though several wrestlers have gotten the best deal of their life in AEW, it doesn't matter much to Vince McMahon.
WWE is still the world's biggest wrestling promotion, and there's no way AEW could take that away from them easily. There's a reason why WWE is at the top. WCW, ECW, and TNA tried to surpass WWE but failed.
R-Truth wanted to 'kill' former WWE writer. More details HERE
Vince knows the value of Ambrose, and it is a reason why he won't let him leave easily. Being WWE's owner, he made billions. So it's no surprise that he can offer a better contract to Ambrose (than AEW) with more creative freedom. And there's no reason why Ambrose would leave WWE if Vince is willing to fulfill his demands.
Plus, there's no other fanbase better than the WWE Universe which could be another reason why Ambrose might not make a deal with AEW.