My observation: Some starts just seem to need peat during germination, and that's sort of a hard requirement. While a lot of things just need better-draining soil (Coir, perlite, etc.), some very slow-germinating but delicate things just don't work well at all without peat. By the time they're starting to sprout, the peat-free alternatives are full of algae and basically rotting.

Thankfully, the use cases are small - I have 20lbs of peat, and it's seen me through about four years and is still half full.