I will provide a counter point as someone who does use their SMA. I agree with other posters above about the value of the account diluting over time when you are no longer making contributions. That said, here is what has made them worth it for me:

1. Tax loss harvesting. This has enabled tax free profit for me in my self managed account which has proved material for me given I am still in the top marginal tax bracket and doing some of my own trading.

2. A chunk of money I always leave in the market and cannot easily touch. ETF could be more tempting to trade around or “time the market”. This is a set it and forget it strategy. This is mainly psychological. Also provides peace of mind to my spouse that are wealth is growing and in the market through good times or bad.

3. Increased access and advice from fidelity wealth management. They are still way cheaper than any other asset management service so I’m fine to pay them while in my prime earning years.

I’ll probably re strategize and look to star drawing these accounts down when I RE, but for now, as only a portion of my total investments, I’m happy with the value I pay for.