Please read the Steem white paper.

SP is a long term investment and should be regarded as such. This ensures that users want to grow the cryptocurrency and vote on what achieves that so the value of their SP is maximized during their 2 year stay (yes, you can get all of your SP back within 2 years if you do it right).

If you don't want that, you have the option of not doing that and just converting Steem to BTC instead.

It's your choice. There's no greed here, just how the cryptocurrency works.

EDIT: 1 year => 2 years