Because signing a guy for 20 mil who would have sold for 70-80mil the last couple summers if Spurs were willing to sell, is really bad business. He's the probably the best player they have now, if he performs to his top level, and getting an extra 4 months of him, while fighting for the scudetto with us, is certainly worth an extra 20mil to them.
Meanwhile, our club, with our CL ambitions, is signing no one to help fix our weaknesses.
Typical Marotta throwing away 20 mil on a world class player though. Shameful.