I dont like a referral system. It is just a financial drain.
Only scams and crappy products need such a thing.
Use the money to spend on something that is actually valuable for steem. We have so many design issues and incentive problems, creating yet another one is not what we need at this stage.
If you want to attract new users invest in a vip or marketing.
Also it is much more important to retain users than getting new ones.
You are right, retention is important and I believe everyone is working to improve that. It needs to be balanced though, on-boarding new user and retention, marketing, UX, innovation, etc...