1 is they're a lot more efficient at producing calories vs calories eaten compared to larger animals, and insanely more water efficient. And 2, which varies by insect, is what they eat and the results of it. Many insects eating habits have positive impacts on environmental health and are sought after for that purpose. Earthworms are a famous example, but there are all kinds of insects that play a composting role in nature, eating decaying organic matter and converting it into nutritionally rich soil for plants. Pollinators are another example.