I think the main assumption is that an advance is forever, while laws and mores and cultures are ephemeral so that a truly useful advance will eventually triumph over any restriction put on it's use.
Certainly there will be restrictions on, say, human organ cloning when we get to that point. Some countries might ban it on ethical or religious grounds. Those consideration totally fall apart when you see the people in Country X being cured of terminal illnesses while yours still die of them. Most nations or political entities will either repeal such laws (people tend to forget that that can happen - they think of laws as something that lasts forever, when in fact they're just speedbumps in a historical sense) or find ways around them. The nations that don't will fall by the wayside and eventually be forgotten.
For some ideas, like the AI or nanotechnology, the regulation idea also falls apart because all you need is one country or one research lab that cares nothing for the law or its restrictions.
Now, another consideration is culture. Some cultures develop things.. and others do not. The bidet is a wonderful invention but how many American homes have one. Some things, even some very useful things, catch on and some do not.
Another consideration is cost. Just because a thing is possible doesn't mean it's cheap enough to enter into common use. We have thermocouples capable of delivering water at precise temperatures every single time. Yet every day, I have to fumble with my shower to get it to the right temperature. We have water heaters capable of delivering hot water instantly to a faucet instead of wasting water while hot water travels from the water heater to the faucet, but I don't want to spend the $600 to install that system in my house.
Another idea is that some ideas just don't work the way we thought they would. Artifical intelligence proved to be vastly harder than anyone dreamed. Nanotechnology will probably never live up to Drexler's vision. I doubt anyone in 1966 would have forseen NASA's budget being gutted, or us not having a reusable non-rocket-based space vehicle in 2005.