When we look at returns for robo advisors vs stocks like REITs, robo advisors have lower yield. How can robo advisors be attractive for me in this case?

I think the main benefit here is passive management. REITs are ultimately still not risk free, and unless you intend to buy into a REIT ETF, you still have to find diversification on your own.

Even when buying into a REIT ETF, note that any disruptions or cooling measures to the property market can severely affect the profitability of REITs, which means your intervention may be required at some point.

The key benefit of robo advisors then becomes clear: truely passive investing where no monitoring is required long term.