Growing plants from seed is the very foundation of every successful veggie garden. If you fail at starting seeds...you won't have anything to show for later on in the season.
Or you have to go and buy in plants which is much more expensive than growing from seed. You also have a much wider choice of vegetable and herb varieties if you buy your own seed.
Apart from that, it is a lot of fun to start your own plants and see them develop from a tiny seed into a productive plant that will produce healthy food for you and your family!
But a lot of frustrating mistakes can be made with seed starting! Seeds are often sown at the wrong time or they rot away because of too much water.