We're sure you've heard some anecdotal stories about young guys shaving their beards for a few years and when they let them grow back in, they are thicker and fuller. You'll have to thank age and natural maturation and growth for that one, fellas - our beards generally fill in and become their densest and thickest when we reach our early to mid 20's, and that is unaffected by how much or how often you shave.
It's a matter of genetics, guys. Love and appreciate what you have instead of chasing the unobtainable. Embrace who you are, your beard, your height, and everything that makes you who you are. When you start to love yourself and who you are, the world becomes a much more beautiful place. Don't hunt down the scams and snake oils - understand that you're unique, you're awesome, and you're allowed to be happy with who you are.