#1 Trophies. Trophies. Trophies
Upon inquiry, several players will say that the genuine and possibly greatest hallmark of one's career is trophies. As many of them as possible.
Money, big clubs, top managers, and experience are all legitimate motivators in football but the most powerful incentive for any player (arguably) is the chance to win silverware. Over the last four years, Real Madrid have amassed a massive haul of 12 trophies, whereas, over the same time period, Tottenham (respectfully) have secured none.
Kane has previously stated his intent for winning trophies and there is certainly time and talent to ensure that he could win some at Tottenham, however, there is a case to be made that he could win much more at Real Madrid with the arsenal of talent and finances available at their disposal.
If Kane were to contemplate a move to Spain, this would arguably be the most probable and convincing reason for him to pursue it.
(Credits: Squawka, WhoScored, Wikipedia)