So, as far as I understand the actual reason that this has never happened and will continue to not happen is that most bugs aren't actually that much more efficient than other protein sources. In fact, for the amount of feed per kg of meat produced, crickets and most beetles actually fall below chicken in terms of efficiency. Worse yet, most of the "able to eat food waste" argument also applies to existing livestock like pigs, rabbits, birds, and cattle, which are already eating that food waste.

Is it possible that there are widely available food sources that are not human edible and efficient to cultivate or repurpose for grub farming? Maybe. But the issue is that without a serious amount of care taken not to waste anything, which may in itself increase waste by way of transportation, it's unlikely that we'll see insects outperforming more traditional small livestock.

I think unless we get to a point where we have limitless clean energy thanks to the wide proliferation of fusion reactors and our focus is on eliminating the last few places that waste water and energy, it's unlikely we're going to see insects as anything more than an alternative to particularly inefficient meat sources like cattle or pigs, and another option alongside things like rabbit, poultry, or fish.