It is because the vote and vote and vote and vote all day long. Some people give this advice to noobs no matter how stupid it is. This is why you get votes from people with 30 rep and 12% power. They are just going all over the place voting for no result.

For me - I think it's best to keep the sp above 75%so there is some small reward from it to me and to the person I am voting for. Slowly - my curation rewards are increasing. I can't buy in, so natural growth of my sp is best. Voting with no sp gives no reward.