This is different for everyone and is not always the choice of the senior and sometimes the responsibility of family or a loved one. There are a lot of different reasons why you could choose to make the change and what kind of change you need to make. Sometimes people are just tired of living alone or living alone is not safe for them due to the risk of falling or emergency situations that would require assistance.
For some going out and being social is not as easy as it once was and doing everyday tasks like meal preparation, remembering medications, cleaning the house, or yard work seems like running a marathon. As a result they are not getting the proper care, their quality of life is diminishing, and their health is suffering from being unable to perform these tasks. Living in an unclean unmaintained home can be draining in itself.
Assisted living and retirement communities offer a good alternative and provide a lot of help that a lot of seniors need or want and puts them in an environment with people just like them. Not only does it help them but it gives them time to do things that they want to do and provides them with the facilities to perform those activities.
It could also put loved ones worries at ease knowing that their loved one is safe and cared for.