A core benefit of robo advice is having a diversified portfolio managed on your behalf. This means that you get a wide mix of investments, unlike people who just buy a few shares and are totally exposed to the UK market only.
Nutmeg are the only robo advisor that currently has a 5 year track record, and the illustration on the left compares the performance of their highest risk portfolio to the FTSE 100 over the five years from October 2012.
£5,000 invested through Nutmeg in October 2012 would have been worth £8,252 5 years later, in comparison to £7,938 if you had opted for just UK shares via the FTSE100. As a rule of thumb, not having all your eggs in one basket should work out better for you over the long term.
Getting someone else to manage the wide spread of investments for you is probably the main benefit of these robo advisers.