Why do the Spanish Football team never sing the National Anthem before international matches?

The "Marcha Real" is the anthem of Spain and 1 of only 4 national anthems in the world, along with those of Bosnia & Herzegovina, San Marino and Kosovo that have no official lyrics.

Though the Marcha Real has no official lyrics, words have been written and used for it in the past. One version was used during Alfonso XIII's reign, another during the Francoist State; but none were ever made official. The national anthem has been played without words since 1978, when lyrics that had been approved by General Franco were abandoned.

After witnessing a rendition of "You'll Never Walk Alone" at Anfield in 2007, the President of the Spanish Olympic Committee (COE), Alejandro Blanco felt inspired to seek lyrics to "La Marcha Real" ahead of Madrid's bid to host the 2016 Olympics.That year Telecinco, enticed by the COE, organized a contest and posted 25 different lyrics on their website which they thought best matched COE's requirements. The winner was chosen, although only 40,000 people voted. The lyrics by Enrique Hernández-Luike, publisher and poet, spoke of freedom, peace and the Constitution.The winning lyrics were sung by the Ronda de Aranzueque choir in Pastrana, and filmed by German TV. However, the COE organized a new competition for the lyrics, which resulted in between 2,000 and 7,000 entries. A private team of jurors chose the entry by Paulino Cubero. The new lyrics received criticism and they were pulled 5 days later, and the idea was scrapped indefinitely.