Sometimes the brand is already secured.. like the @crowdfunder business plan I submitted @choogirl.
https://steemit.com/steem/@chrisrice/creating-a-start-up-on-steem-or-crowdfunder-xyz
And in that case, I cannot do it on my own but publishing it on @aggroed's contest might get the attention of investors or future co-founders that can help me get the idea off the ground.
The reward of 100 Steem + 50 Steem from @cryptoctopus can also help me get started!
And finally, there are also cases where a person has a really good idea but is incapable (or maybe unwilling) of doing it. In that case, it is better to submit the idea, help the community and win the prize money.
I have another good business idea that I'll submit to this contest soon, and if I start @crowdfunder I will continue to submit business ideas.