Two people who want to build a life together have often gotten married and spoken their vows formally, in front of friends and family, as well as obtaining a marriage license to cover the legal aspects of their union. While that was the path usually taken in the past, couples today have many reasons to make a commitment without legal entanglements. This applies to younger people, but it is often necessary for those with plenty of life experience.
Retired people have usually had a previous spouse, so t he idea of making a commitment to another person is something they can do with full knowledge. There is no lack in their ability to make a decision, and they will follow through with it faithfully for the rest of their life. The reason they would rather skip the official licensing requirements is often due to the terms of their pension or other legal matters having to do with retirement income.
The modern answer to these issues is to remain legally single and have a commitment ceremony rather than a wedding. Friends and family are invited as witnesses, and there is an officiator who orchestrates the affair in the same manner as a normal wedding. The couple chooses their own vows, or they might opt to use traditional wedding vows. It is the formality of their vows to each other that is the important part of the ceremony, and the form matters less than the commitment of each person.
Modern life has changed the way people look at the world around them, and they have begun to choose less traditional ways to live. The ability to find and commit to another person is not new, but the way it is done has become more of a reaction to modern life than to the tradition of taking vows as a couple. Commitment ceremonies are about joining two lives in the same way marriage ceremonies have been performed for centuries.