I'm not sure I understand why that is. The argument is that scale is the biggest limiting factor, but I would think achieving scale would be so much easier. A million crickets is a lot easier to house than even a few hundred steer. I really want to see evidence that insects are sustainable and affordable as a food source before I dive too far down into that particular rabbit hole.
I'm a vegetarian for ethical and environmental reasons, but I'm not sure my ethical stance extends to include insects and arachnids (though I do take them outside rather than kill them). I already occasionally eat clams and scallops and oysters. I'd probably eat bugs, if they were sustainable to farm and if they were not for economic elites only; I also tend to opt out of luxury economies on ethical grounds.
But don't take my word for it; try it for yourself -- next time you find that a spider's spun her web in a corner, leave her be, and you'll likely find yourself less frequently called upon to escort importunate insects out the door; she'll be happy to take care of the problem, to the benefit of both of you.
Also, one time I came back to my motorhome after staying with family for a couple of weeks and found thousands of baby spiders crawling around on and hanging from the ceiling (and on my face and in my hair). That was another instance where it was me or the spiders, and the spiders got swept outside. I feel no remorse over this decision.
So you might find an ethical niche in there.
So, my decision to eat bugs would be considered on the ethics of the question, among others: Is it environmentally sustainable (and, in my case, it would need to be equal or greater than the sustainability of a plant-based diet)? Is it ethical (probably just whether the bugs suffer)? Is it healthy? Is it tasty?