For friendlies, it might be a rotational duty of sorts. 1.5 million shares = a few hundred thousand dollars = minor income to pay some NWBO bills. The exercise does not raise share price though....and it does not need to be scrutinized as possibly insider info, because it is just a warrant exercise. Think of that what you will.
I think there is only one (other than private and personal needs for money now etc.) is if the share price has gone up a lot, and you are afraid that some (much) of that value will be lost back as the stock retraces lower if you continue to wait and you wish to capture all of the present value before it is lost.