I believe PPV sharing is probably the main reason why they haven't come up with a deal yet. Spence's previous PPV buys are a little better than Crawford's. Spence also has more belts to offer in the division but Crawford is the only ATG of the two.
There's no other reasons, Crawford here has to agree with a small share because Spence will not agree with a 50/50 share.
he has more belts and he has a better PPV record in the past compared to Crawford.
We get it, Crawford is also a champion but Spence have proven enough based on the numbers he have.
However, Spence versus Crawford might be the biggest payperview revenue in the history of boxing. It might be more than the payperview numbers of Mayweather versus Pacman. It would be very stupid for Terence Crawford's team to not demand a share equal to Spence's share.