I belong to Smarta family.
Till photography became popular in India in Mid 19th century and selling of photos/colour paintings of Gods had become a commercial business, idols of Gods were used to be worshipped.
Way back in late 1980s, when I was still in early twenties, I had observed in houses of our relatives and family friends, people of old generation,ie., of 1900 - 1950s, used to keep picture of female TRINITY, i. e., Saraswati, Lakshmi and Parvati in a single picture, in their houses.
This devotion to female TRINITY is prevalent in the families, who are regular reciters of Devi Mahatmya or Durga Saptasathi. In Durga Saptasathi, which is a part of Devi Bhagavatam, Devi has been eulogised as the eliminator of Mahishasura, Chanda, Munda, Nishumha, Raktabhija, Shumba, etc. Lakshmi, Saraswati, and Durga will be eulogised while reciting certain chapters.
I don't want to quote folklore like this of adoring Lakshmi and Ganapati together.
Certain people, especially from business community, might have popularised the image of Lakshmi, Ganapati and Saraswati, removing Parvati, as they are more interested in getting obstacles removed while doing business. As Ganapati is the son of Parvati, the latter might have been removed.
In some families, Ganapati will be worshipped even before doing Saraswati puja for children.