Filipinos are respectful (magalang).
It is common among Filipinos to call someone who is older Ate, Kuya, Tita or Tito as a sign of respect, even if there is no blood relation.
I call the parents of my good friends Tita–Tita Lorna, Tita Mildred, Tita Edith etc. My children now call my best friends Tita too–Tita Chelle, Tita Raquel, Tita Irma, Tita Mako etc.
My parents, although very friendly and warm, were very formal. We addressed their friends Mister and Missus—Mr. Villanueva, Mr. Pineda, Mr. Vergara, Mr. Pagsanjan, Mrs. Gabaya. I only got comfortable using Tita when I heard my friends call my mom, Tita.
Now that I am living in the United States, I am torn between having my children use first names for my friends, which is the American way, and having them use Auntie (or Uncle), which is the Filipino way.
I don’t think Filipinos living abroad would find using the latter strange, but I could imagine how foreigners would find this bizarre. I am friends with grown children of American and European descent who call their parents and parents-in-law by their first names.
I figured that unless my friends insist that they be called by their first names, my children would address them respectfully by using Mister and Missus, Tito and Tita, or Auntie and Uncle.
“Good Morning, Mr. and Mrs. Smith, may I play with Johnny?”
“Tita, can I have a playdate?”
It is after all, the Filipino way.