Why not bring people to invest?

Why can't they hold onto spot assets?
Most people think making money is 1w…3w…10w…20w…50w…100w～
But real investing is 1w…−3w…−20w……5w……-10w……30w such numbers.
Who would really bring someone along? Can't hold on? When the principal loses 10w or 50w, they've already turned against each other, exchanging harsh words!
Bringing someone along to make 100w, just a thank you and it's over.
Losing 10w, they’d be furious and hold a grudge for a lifetime...
Making a living through investing and trading—only managing their own account.