I dont use free if the product my website is advertising isnt free, otherwise its a lie. Use free only if its free, not just to get disapointed visitors.
I you are looking to get rank with visits like Alexa then you have to use Free .. Even if you are selling products or let say 3D models you can get guest with the keyword "Free" and then maybe they will buy from you ..
i have to use it for my site as it is about free live streaming but then i think when free comes on to website page, google adsense doesn't pay alot i need to get 300clicks to earn $30
Yes, using free + keyword helps a lot especially in rankings. If you are focused on profit and nothing to offer for free then you should not use this feature just to generate traffic. You only make your visitors disappointed.