Soup spoons are designed for eating soup. They hold a mouthful of sloppy soup, carry it safely to the mouth, and can be tipped into the mouth sideways.
Dessertspoons are not for soup - they are for more solid stuff and they have to be put into the mouth square on - which means your elbow has to stick out. Try that with a dessertspoon of liquid, and you are likely to get the lot in your lap, particularly if the table is crowded.
Tablespoons are not for soup, they are too big to eat with. For some reason, some restaurants seem to think that a tablespoon is OK for eating soup. It is not.
Dessert forks are for breaking up desserts - a spoon alone is not sufficient for a dessert with pastry in it and trying to break through with a spoon can send shards across the table.
A piece of cloth laid across your lap is to catch anything that does fall before it hits your clothes - and postpone laundering them.
And so on and so forth. Go back a few hundred years, and you would be eating with your own knife (kept in a sheath in your belt) with a horn spoon for soups, plus your fingers of course. All these new implements came into use to make eating a cleaner, more civilised activity.
People now think that is outdated.