I don't know what are Wealthfront's fee, but not everyone wants to put all their eggs in SPY. Wealthfront (and other similar services) let you pick a risk score, and based on that invest in lots of different things. Most people have very diversified Wealthfront portfolios. They also claim to help with tax harvesting. Since SPY had an amazing run it performed better than your friends' accounts, but it doesn't mean it will keep outperforming in the future. It's a riskier investment.

Now, obviously you can also create a very diversified portfolio by yourself. That's totally fine if you know what you're doing and OK spending the time doing it.