They already have done that with the addition of 0.5 moons. What you lose in yield, you gain in convenience of not having to warp to a safe every time someone enters local*. You’ll still make more in null-sec, if you’re mining a moon with good moon ore in it - the ones available in high-sec are only the gases. Get yourself a Loparite/Monazite/Xenotime/Ytterbite moon in null and you’ll do far better than a high-sec miner. It’ll just be from moon goo rather than minerals.
*Assuming Local is actually working at the time and the chat server hasn’t crapped itself.