Because a lot of the time they're not.

I'm sick of all of the movies that show the gods sitting around calmly and regally.
Read any little bit of mythology and you'll likely find the opposite.
They're petty.
They whine.
They fight.
They punish mortals for things that aren't the mortal's fault.
(Someone else said she's prettier, or more skilled.)
They punish mortals because they didn't offer enough, or the right things.
(Or because they built a wall on the beach without asking.)
Those are the real gods.
Not the serene, level-headed guys and gals sitting around having tea.
(Okay, so I don't think I've ever seen them having tea, but still.)
Honestly, the more I read, the more the old Hercules and Xena shows seem much more realistic.