>> Starting indoors is for people with short seasons...
And for impatient people who want the EARLIEST POSSIBLE vegetables or blooms.
Starting indoors or under plastic can also help to protect small seedlings from slugs (they LOVE Delphinium seedlings but leave big plants alone). Or insects, seed-eating birds, and seed-bed-peeing cats.
I also keep losing all my peas to rot if I start them outdoors too early (cold wet clay and rain every day). Pre-soaking, pre-germinating or even starting in guttering under plastic solves the early-rot problem.