Most are based on organophosphates, which work basically by sending the nervous system into hyperdrive. They will kill a wide swath of animals (not just insects) if applied heavily enough. Some are deadlier to certain insects more than others. For example, Sevin kills bees even in very small doses.

The other thing to note is that "loss of habitat" isn't always disappearing wetlands or stands of trees being cut down and converted to tillage. The widespread use of herbicides has almost eliminated milkweed in areas where it used to be very common, for example. When I was a kid, it was everywhere in the ditches of the Midwest. Now it's rare to see it. Milkweed is essential for monarch butterflies.

Also these ditches and edges of farm properties are often eliminated with consolidation of farmland into larger and larger continuous acreage ownership.