Life is unexpected, and it is important to have a plan in place for the "what-ifs" in life. What if you become incapacitated (unable to manage your financial affairs)? What if you pass away? What happens then?
A plan allows you to choose who will step in to act on your behalf when needed.
A "plan" generally consists of a Living Trust, a Will, a Financial Power of Attorney, a Advanced Health Care Directive, and Funding Documents. These are all tools that are ready to be used in the event they are needed. If there is an event (car accident, stroke, the slow decline of age via dementia or Alzheimer's) in which someone needs to step in on your behalf, and these tools are not in place, then a court will get involved and make decisions for you. You're spouse is NOT automatically given authority to manage for you!
A proper plan can avoid court involvement (conservatorship or probate) and keep you in control.