Glory
When your forecasts of the future are on the money, there'll likely be more money in your future. Aside from the prospect of a bonus or bump in pay when you've helped a client reap financial gains, you have the satisfaction of knowing that you've done a good job and made someone extremely happy. In that sense, you're sort of like an ice cream man. But only in that sense.
And, of course, if you do this often, it's likely that a hedge fund manager or other buy-side player will come to you and offer you a wallet. If you make that wallet grow fat, you keep a percentage of the upside, and that's where most of the "big money" comes from in today's Wall Street.