They also use to fuck little children and animals. It was just seen as a hobby and not as a sexual orientation.
The Spartans each had male partners, who they had sex with, so it was part of their sysyem, not just a hobby.
It was also considered 'normal' for Macedonian men to have have male lovers when they're younger until they get married to a woman at about 30.
I was reading 'Hiero the Tyrant' by Xenophon (In the Greek world Tyrant means King) and and every reference to a relationship sex is taken for granted to be with a male partner.