My mother had wanted a statue of Mary outside our house for years. One year, her sister finally got her one, a beautiful statue of Our Lady of Grace. My aunt had gotten one for herself and each of her sisters. My mother loved the statue and very happily set it right in the very front of our garden. Due to the frequent torrential downpours in Florida, it was not rare for one of us children to be sent out with the express order to "Go save Mary!"
Catholics have been putting statues of Mary and the saints outside their homes for years. St. Francis is a common occupant in Catholic gardens, as well as non-Catholic gardens, due to his being the patron of animals and the environment. St. Michael is also a popular choice for his renown as a defender of the Faithful. Many find they like St. Joseph in their front garden, or in the ground if they're selling their house, as the protector of the Church, Holy Family and patron of those selling their homes, seeking his intercession to protect their own family. A statue of Mary is very familiar outside of Catholic homes as the inhabitants seek to create their own Mary garden.
Regardless of preference, outdoor statues have found their place outside Catholic homes for years as the families inside seek the saints' or Blessed Mother's intercession in protecting their homes and gardens and asking that those inside be aided in their search for holiness. To many, they are a sign of devotion and reverence and will continue to be for many years.