Why is using can tomatoes versus fresh tomatoes preferred when making marinara sauce?!

Tomatoes are canned when they are at their peak. Using canned tomatoes ensures you will have ripe tomatoes every time you make sauce. Using fresh tomatoes may not always be good. They coast more and are not always the tastiest especially out of season.

Also when using fresh tomatoes you would have to pass the tomattoes though a food mill to remove the skills which is extra work.

So the skins are puckered and broken down. If you don't, then you would want to blister the skins of fresh tomatoes in the oven or by poaching.