'company's picnic', or 'company picnic'

[wotcha]

"Rain poured restlessly, dampening the company picnic"

My grammar book says 'company's picnic' is grammatically incorrect. Why is that?

 

[Barb_D]

I think to call it incorrect is overstating it.

We tend to use nouns, in the singular, to modify other nouns instead of making them possessive.

Shoe store
Faculty lounge
Table leg
Car door
Company picnic

However, there are times when the phrase "company's picnic" would not only be okay, it would be preferable, such as when several people are comparing their experiences at the picnics held by their respective companies.

 

[Rover_KE]

I'd have said 'Rain poured relentlessly.

Rover