They're inconceivably useful, the perfect size for everything

• mise en place
• egg cup
• souffle (I've never done this)
• secret late night peanut butter + chocolate chip
• microwave one serving of leftover tomato sauce
• spoon rest
• dipping sauce because fuck those tiny plastic cups, homie
• beat a single egg
• whipped cream decanter when you're fancy
• Lego and gunpla part sorting
• spider cup
• melted butter
• fart noises with your hand
• muffin stuff
• egg sandwich... Okay this is just egg cup with bread my bad
• a weirdly small amount of grapes
• single serving of cookie dough
• cinnamon sugar mix for tortilla elephant ears

if you're a parent, you already have these.
it's your kids' bowls that they eat out of. just buy a few extras, preferably the ones that come with snap-on lids.