Is it necessary to add lemon juice in homemade raspberry filling? What does the lemon do for the recipe???

I make it without.   I have always yielded a great result with nice color. 

The only thing I can think is adding lemon juice may help to inhibit bacterial growth as it makes the PH of the filling more acidic? (I am taking a guess on this.  Although some bacteria can thrive in a more acidic environment. Plus depending on how much sugar the recipe calls for, the preservation process is achieved by that which also inhibits bacterial growth)

the other thing I can guess at is for color and flavor.   Lemon juice is added to some fruit to help stop the browning that occurs.   The lemon would also add a bit of tart depth to the raspberries.  (But they are pretty tart on their own)

All of the recipes I googled called for lemon.....