It is not scalable and it take work from the brightest minds, so the investment returns is more like a salary.
“It’s a different sort of place. ... We have 25 people in the office,”he says of the small Berkshire Hathaway headquarters in Omaha, Nebraska. “And if you go back, it’s the exact same 25. The exact same ones.” https://www.cnbc.com/2017/05/22/surprising-things-in-warren-buffetts-office.html As per his authorized biography "The Snowball" Buffett makes all the investment decisions singularly; to be fair though both in the investment realm it's a completely different kind of business than Simons'.