Risk management and asset allocation that matches changes in your personal life and your risk profile.

For example: If you know you need to use $200,000 within next two years, you might want to start moving part of that sum slowly from stock index fund into other less volatile assets (like bonds etc).

You can do that for yourself approximately without knowing about theory, but if there is cheap automated system that can provide personal solution based on portfolio management theory with few bucks, it's can be worth of the small sum they ask.

Rebalancing, tax loss harvesting, and asset allocation as you grow older (i.e. more weight in fixed income as you approach or are in retirement.)

The most important advice is to stay the course and leave your investment alone. I read somewhere that the biggest gainers at Fidelity (?) were those who forgot they had an account at all.