When my son graduated from college and was soon to be married, I was thinking about the timing of cutting ALL those strings, and he went ahead and did it all for me.
Got his own cell phone plan, insurance, bank accounts, you name it.
He took the initiative and did it all on his own.
At 23 years old.
My younger daughter also has been pretty proactive on being on her own. My older one needed a little prompting, but she was in a more difficult financial situation and needed better health ins than obamacare.
My wife and I came of age in the 1970s and back then, it was considered embarrassing to live with your parents if you were grown up and not in college. My wife (years before I met her) got an apartment and subsisted on boxes of Mac & Cheese and Hamburger Helper for a while. But she was proud to have her own place and become independent at an early age. For myself, I joined the military at age 18 - which I guess is kind of cheating because the U.S. government took care of me for a while. But I didn't go home after my discharge, I lived in ratty apartments for a while until I could afford something better.
This "arrested development" for our young adults can't be a good thing. I think this is why they have trouble emotionally when they run into adversity.