Isn't it awesome? I'm new to 3D printing and modeling as well (just got my first 3D printer at the end of February) and Pinshape already featured some of my designs! They even tweeted about them!
I doubt I'll ever become a "professional 3D designer" or anything like that but it feels great to have your art/functional designs showcased like that.
I also find the contests inspiring. For example, I'm not a mechanical engineer but when I saw some fidget spinners entered and accepted into the mechanical design contest I thought, "why not?" and entered my own. I even came up with a wind-powered mechanical "Invincible Lawn Star" (haha) specifically for the contest.
If it weren't for the contest I might not have come up with such a cool thing! My neighbors have already inquired as to, "where'd you get that cool star?!?" and "where can I get one?"
I'm already working on an Independence Day themed lawn star spinner =)