If the unthinkable happens, most people would be comforted knowing that those they trust can be in charge of their health and well-being when they're unable to do so themselves. Although the UK has substantive laws and practices to protect the vulnerable via the Court of Protection, voluntarily putting Lasting Powers of Attorney in place can bring this peace of mind to those less inclined to leave decisions about their welfare in the hands of (albeit competent) strangers.
LPAs for Health and Welfare allow you to nominate 'attorneys' who essentially can step up and take charge if you lose the mental capacity to do so yourself. The attorney(s) can be anyone over 18 who you trust to act with your best interests at heart and they can make a number of decisions for your personal care, be it medical decisions, living arrangements or participation in social activities. If the worst should happen and you require life sustaining treatment, the LPA can give your attorney(s) the power to make decisions in this regard. Without an LPA, these decisions are made by health care professionals and can frequently take a long time to come to head. This is entirely understandable given the gravity of the decision, but still makes it no less painful for any loved one to endure, particularly if it's contrary to what they would have chosen.
It's not a pleasant topic to think about, but being able to assert some control over the uncontrollable will be a comforting thought for many.