Logic please?

A fleeting thought I have absolutley every time I use the metro (which would be twice a day, atleast) is: why the hell doesn't any metro station in Madrid have a bathroom?!

Running from one side of Madrid to the other all day, it almost makes me mad when I can't run to the bathroom for a wee in between. I have to find a coffee shop - where until recently I felt bad not having a coffee and just using the bathroom - but now I don't give a shit. I was spending too much money on coffee that I didn't even want to drink.

In a capital city with a population of about 4 million people, atleast half of whom take the metro twice a day if not more, why wouldn't you build toilets?