Blood moons early game are threatening and dangerous, but a good opportunity to get good loot like the vampire frog staff, money trough and shark tooth necklace. Plus, early game blood moons are less likely to happen when grinding or building. Later on, they become intrusive and halt sleeping or mess up building, and become less essential, however they’re still important to magnify spawn rates or for some very specific items.
I’d personally make them much more likely to spawn the first time, but put it a bit later into prehardmode progression, but after that make them less likely (or impossible, but that’s a bit less interesting) to occur randomly and let you sleep through them, and give players another somewhat reliable way to get bloody tears outside of Blood Moon.