I have at least 6 flying pollinators working my greenhouse, wild bees are just one of them. For some strange reason there is a widespread belief that bees are the only pollinators out there.
You are right that there are many pollinators. Hummingbirds, butterflies, bats, many species of insects, wind, and even rainwater, are all essential to pollinate some plant species.
The focus on the honey bee is many economic. Where there are many hectares of a single crop, all blooming at the same time, there aren't enough natural pollinators available. The honey bee is usually the most practical to import temporarily for pollination services. We wouldn't have much of an almond, apple or blueberry crop without them.
However, some species of insect-pollinated fruit have flowers that are not attractive to honey bees. Sometimes the flowers have inaccessible nectar or flowers that are too small.