It would seem it started as a sign that Spiderman was getting is own saga in the MCU, also allowing for multiple meanings behind the title. From this Cinemablend article on Far From Home:
After all, while part of the title is referencing the fact that the film features a homecoming dance, it was also a clear nod to the fact that the hero was finally getting his own Marvel Cinematic Universe feature.
And then they just liked the idea of keeping the world "home" in the title as a theme.
And we liked continuing the 'Home' thing, with the little Spidey symbol in the 'Home.' -- Kevin Feige
Fans have been trying to guess the name of the third movie, and the studio and cast played with the audience revealing fake names, then releasing a fun video for the actual reveal of the title where the three main stars talk about how the director doesn't trust them with the secret because they would spoil it to everybody.