Why invest in $BRK when the S&P 500 exists?

I know Berkshire Hathaway, is popular and considered a strong stock, and I myself have been interested in it for a while. But why invest in $BRK when recently it has basically followed the S&P 500? Hell, even Buffett himself has told his wife to put their money into the S&P 500 when he passes.

Why put your money into a single stock (Berkshire Hathaway), which increases risk, when you could put it into the S&P 500 for pretty much the same outcome?

This is a genuine question. I don’t hate the stock, and in fact I am bullish on Berkshire – but I’m also bullish with the 500 too.