Using a type of artificial intelligence known as deep learning, MIT researchers have discovered a class of compounds that can kill a drug-resistant bacterium that causes more than 10,000 deaths in the United States every year.
Healthy people with access to the surrounding world through the Internet is a giant net positive for a country
Certainly, if that was all the public domain was, it'd be great! But it's much worse than that. It allows people to freely take and profit off the art of others without paying dividends. It allows larger companies to steal and copy designs of small, new companies and under cut them even more readily and easily than they already do.
There's plenty of downsides that you're not considering.
Private just makes more money and also you can do ridiculous shit like blow up your own rocket, destroying a landing pad in the process and ignore environmental and labor laws.