Think about it... you are getting standard edition for "free". Google wouldn't do unless some non-trivial number of users is READING and CLICKING on those ads. If your secretary is working on a budget spreadsheet, and gets distracted by an google ad in the corner of her spreadsheet, gets distracted and clicks on it, and goes browsing for 20 minutes as a result... that costs you money. And THAT is PRECISELY what your beloved partner google is counting on. THAT is their entire business model. Give you the app for free, and then extract a profit by luring your staff to click ads instead of work.
There are no ads in google docs.