The National Archives charges you for copies of these records, as does Cook County Illinois. You don't own your birth certificate, the state where you were born owns it and has complete control over it. Ever try walking in there and telling them you want to change parents? They're not going to take out a bottle of White Out, retype it and just hand it back to you.
States, counties, shipping companies, and National Archives around the world COOPERATE with Ancestry...but they're paid for the access to their records. You CAN find many of these databases online somewhere else for free. But you have to know where to look for them. The convenience of having them all in one place comes from licensing fees that Ancestry pays. It's no different than your local radio station playing songs by artists from around the country...and paying a royalty to that artist for the privilege of playing that song on their airwaves.
Ancestry had a long, hard road to get to where they are right now. For about 4 years I walked away from them altogether. They didn't have their act together and they didn't have many good datasets. But they persevered and worked on those federal and state contracts. They also had to pay for those contracts. Some comes from advertisers, but most comes from membership fees. I remember the annual membership used to be $49.99/year. That changed as their costs went up. Like any other business, they can't operate on goodwill. They have to pay to play, so we have to pay to play.
If you want to search census records for free, go to the nearest LDS Family History Center. If you want it from the Internet, only 1880 is "free". Bits and pieces of others are available, but not with a nice cushy index and all the bells and whistles you're used to. It took many of us YEARS to transcribe all of those records. You might find a local county's records on GenWeb, but don't look for 80 years worth of records for free anywhere. There were hundreds of thousands of hours put into that project and they still haven't recouped their costs.