If something happens to you and you become incapacitated and unable to make your own decisions, don't you want to know that the person making choices on your behalf really has your best interests at heart?
Legally speaking, unmarried couples are not "together." You can live together for 20 years, but, unless you officially tie the knot, the state does not care.
It used to be that all wills were written by hand. Today, though, most are typed out. Often, you have both electronic copies and paper copies.
If your elderly parent sets up a legal power of attorney for you, it gives you a lot of options to work on their behalf while they're still alive. You get to access their bank account, pay their bills, pay taxes and do many other things of this nature.