Why does he feel that he has to be financially secure before getting engaged?

My bf and I have been together for 3 years and 4 months. We've been living in an apartment for 9 months and will be taking our first real vacation to Baltimore, MD in 4 months. I'm so excited! So, I've been so impatient about this whole engagement thing. I don't expect some huge, expensive ring that everyone will envy! I chose a few inexpensive art-deco rings that I really like for him. He feels as though we need to be financially secure before he can do this. He's not sure if he's emotionally ready to marry me. We talk about wanting a future together. I love him more than anything and I don't see my self with anyone else. He's the one for me and I knew it the moment I met him. My plan I had in my head was 4-5 years and then engagement. Then 1-2 years to plan and then marriage. I want 1 child with a small house and a dog! It seems to be both our dreams. Right now we're both in jobs we basically hate, but are not soon to be fired from. He's a great worker. He just doesn't like the work. I would be no where without him. I am willing to put in the time and effort to save for our house and future lives. I wish this impatient feeling would go away!!