Sugar spikes also give people brain fog, tiredness (so they sleep during the day after meals), worse memory, worse concentration for example in work, it causes sugar cravings after it leaves the blood (and therefore snacking) and, of course, sugar damages teeth. Also, fructose causes similar problems in the liver like alcohol. In blood, sugars bind to proteins and damage red blood cells or stem cells. Etc.
And, people forget, sugar is addictive. So consuming a bit of sugar leads to consuming more sugar. Without much of exaggeration, in most people, fruit, bread or potatoes will lead to sweets and colas, in time.
It also supports most kinds of cancers (cancer cells lose the ability to utilize fats as energy, so they need dietary sugars to divide), makes intermittent fasting harder, it influences mood and may cause anxieties....
Really, from the nutritional standpoint, its hard to defend why to put any eat sugar into mouth, at all.