Steemit is a money printing machine?

I'm here roughly around a week now and I just found out that we get reward for curation because I just got paid once for curative reward although I upvote a lot of post. At 1st I thought there's some fees that steemit will deduct from post like 40-50%. I'm not very good at all the crypto currency stuff but isn't it suppose to be created because it's more stable than money? My question and worry are

When we upvote a post, we are making new steem dollars each seconds which roughly totalled around 80,000 steam dollars each day or more. No one is losing any steam dollars, we just upvote and create new ones. Is it sustainable in the long run? I can understand Bitcoin because there's a cap at 21 million and that's why it's valueable. Is there a cap for steem? And we get steem power interest every min or so. It's like a unlimited money making machine constantly printing money with no limit. More steem in the market means less valueable. No? Can someone please explain to me in simple words how this thing can work? Thank you so much.