So the bible finds sex tolerable?
Did you think christians to be asexual?
Please cite scripture that says they were not married.
Even if there is; it is poetry. Poetry that a couple found exciting. Extremely metaphorical poetry that a couple found exciting.
With as metaphorical as it is; nothing is says can be safely taken literal.
The point of the book is to show that god condones sex. And he encourages us to take delight in it.