What's the deal with sugar in ketchup?

I've heard for years and years that ketchup has a lot of sugar in it. Why does that matter? Who is guzzling all this ketchup? I only use a tiny amount. I only need one packet if I'm eating fast food and I use it for fries or hash browns. But everyone's like watch out! Ketchup has sugar in it! But fries are made of potatoes and potatoes are made of starch and that's just chains of sugars, and then you're probably drinking soda with sugar in it, so is the ketchup really going to make a difference? Do some people just slurp the stuff straight out the bottle?