To Ketchup or Not To Ketchup

When Mom T taught me how to make meatloaf, back when I was a new bride for the first time, she insisted that one does not put the ketchup* on the meatloaf while it cooks, only afterward, at the table. Since her meatloaf, a bumpy, chewy feast of textures and flavors, nicely caramelized and guaranteed to encourage overeating, is still my gold standard, I have always followed her dictum.

Lately, however, I've begun to question this doctrine. Meatloaf lovers, I'm curious - do you add the ketchup while the meatloaf is cooking, or not, and what is your reasoning for doing it whichever way you do?

Mom T's Meatloaf

2 lbs. ground beef
1/4 lb bulk sausage**
1.5 slices bread, torn into small pieces
1 egg
1 medium-large onion, chopped
1 or 1 sticks celery, chopped

Sauté onion and celery until soft. Add to other ingredients in a large bowl and mix thoroughly with your hands. Push into a shallow baking pan (it should be about 2" thick) and bake at 375 degrees for about an hour, to desired dark brownness. Serve with ketchup, preferably the sublime ketchup* that June Taylor makes.

**I realized upon typing this out that I have made a modification to her original recipe; I use 1 pound of ground beef and 1 pound of sausage, either bulk sausage or sometimes spicy Italian sausage. I also use whatever bread I have around although she always used sliced white bread.