A lot of people nowadays can handle their own investments and money by themselves through the use of the plethora of providers and information online.

Where I would say advice is key would be:

• If a person is anxious of investing and really needs a guiding hand
• someone just really wants nothing to do with their finances and are willing to pay for that to be looked after
• tax advantages (this particularly for higher net worth individuals
• estate planning

Perhaps if you ar unsure of anything and you have quite complex/large finances you could get a one-off meeting with an adviser and get advice on planning etc.

If currently you are just investing in index funds in a S&S ISA and are happy with that, then really there is no need for an adviser at that point.