These two teams have maintained a high level of competition for a long time, which is very attractive to excellent football players. Now the two best players, Cristiano Ronaldo and Lionel Messi, play for two teams respectively. At present, many Spanish players rank first in the national team, such as Xavi, Iniesta, Ramos, casillas and so on, and also play for these two teams.
The underlying reason is that the business model of these two teams is membership, and members of the membership team have to pay fees. Their purpose is not to make money, but to improve the competitive level of the team. Therefore, the team's income can be fully invested in the transfer fee and player's salary, which is very attractive to professional players.