People that don't invest in themselves don't do it for one reason and one reason only. They don't believe in themselves. They don't believe the $10they spend on a book will give them any new ideas to improve their life. They don't believe the $500 seminar on improving their business, will do them any good. Same goes for health. They don't think highly of themselves enough to invest in eating healthy or hiring a coach to help lose the weight.
The most successful people I know look at a $10 book as a possibility of finding one idea they can turn into thousands of dollars. They'll happily spend $500 on a seminar, not just for knowledge, but to grow their network with other success minded people. They emphasize their health to maximize their levels of energy and confidence. They believe everything they invest in themselves will be returned to them x 1000000.
Believe in yourself. Because you'll never be able to bet on yourself if you don't. People who don't bet on themselves are satisfied with being average. But you're on my email list, so you're not about that life. Follow the advice of the great Jim Rohn, "Never wish it were easier, wish were better."