Delegation of Steem Power can be good and bad.
If you don't have the time (or desire) to manually curate, donating some of your power to someone who has similar values to yours allows you to vote by proxy.
The downfalls you mentioned above are all true. Upvotes (whether original or delegated) can all be abused.
For myself, I Steem close to full time. Someone has been kind enough to delegate power to me, so I curate based on value I find in other's posts. I always curate manually and I know I'm not abusing the system.
For some, delegation toward "bought" voters is a mixed bag of good and bad. I recently wrote a post suggesting that minnows use the bought votes to support each other instead of themselves. Sometimes the "bought" votes are used to promote crap and other abuses.
Overall, delegation has good and bad purposes ... but so does Steem Power in general.
Good point, I agree. Thanks for your comment.