Some of it is probably personal preference too. I really like cinnamon, which might influence why i like it particularly much in tomato sauce ^.^
Typically for tomato sauce I like it quite umami, so I add things like peppers (the fruit/veg and black pepper), soya sauce, salt, MSG, etc., as well as mixed “italian” (i doubt it actually is, but it’s sold as that, and I have limited spice cupboard space) herb and spice mixes (usually with stuff like parsley, basil, etc. in it), as well as sage, thyme, garlic powder, with amounts depending on what I want ^.^
Probably the only time I wouldn’t add cinnamon is if I was using the tonato sauce as a component of a curry, but a lot of that is because it would get diluted out and I don’t think cinnamon goes so well with some curry flavours.