Why do I have to stake tokens in order to vote, and why are they locked?

As a holder of VITA tokens, you need to stake (some or all of) them first in order to be able to vote. Moreover, once you cast a vote with a number of staked tokens, that number of tokens remains unavailable for further voting until the voting period of the proposal has passed. At any time, you can only use tokens that are both staked and not locked for voting.

Note, this may affect your voting strategy. Unless you intentionally want to cast all your votes (i.e., tokens) on a single proposal for the whole duration of 14 days, you may want to allocate your staked tokens across multiple proposals according to the subjective importance of all proposals over a 14-day period.

Staking and locking are safety mechanisms necessary to prevent voter fraud, when otherwise someone could vote with their tokens before sending them to another wallet and use the very same tokens to vote again. (Traditionally called a Sybil attack.)