Your personal finance structure may have changed negatively over time. Consequently, you may not be able to afford your home anymore. Selling quickly can avoid the chance of a foreclosure.
life changes are the reason for most home ownership changes - downsize as children grow up and move out on their own or up-size family begins to grow and they need a bigger place to raise their families. Divorce - as couples liquidate their home and split assets. Inheritance - need to liquidate an estate of a deceased family member.
Your family is forced to relocate for a better job opportunity or a mandated company transfer. This person really has to sell quickly because moving, starting a new job and selling a house is overwhelming. Some people relocate because of military deployment or imprisonment.