The families I know (very small sample set) that have successfully transfered the investment management from one generation to the next were large enough that they had a platform of bankers, portfolio managers, etc. The family members acted as asset allocators and specific individuals would often go to a sector that interested them: real estate, hedgefunds, etc. Those families are 9 figure families. I don't understand why the new generation doesn't want to run manufacturing companies (regardless of their size or sophistication). I see it a lot. Business owner is retiring and no one in the family wants the business. This is especially with small owner/operator businesses.
Because the media has glorified banks in order to keep their psychological hold of today's youth and breed them to accept banks being institutions in size that you and myself never would have dreamed of as a kid. Manufacturing in the U.S. is also a joke. Government is corrupt. Large businesses regulate the small ones. Regulators are corrupt. All the taxes, fines, penalties, licenses, etc. coupled with the constant attack on small business in America makes it extremely undesirable. My generation (which were born in the 60s and 70s) have allowed the country to be taken over by special interest groups. It all went down hill after JFK's assassination. On top of this, the younger generations are less-educated, ignorant to reality, and have grown up in a world where they do not interact socially but rather get their views of society based on things like TV, Ipads and computers. As for trading as a business, it is done by many but you have to treat it the way you would treat any other business. If you aren't able to keep your emotions and check and be disciplined, it's very easy to fail in any type of business but especially easy to fail in trading because you can lose all your $$ with a few clicks of a mouse and no physical asset is involved.
Don't diss manufacturing in the US. US is producing more than it Ever has. Just with fewer jobs and people. A good manufacturing company can be bought for an implied IRR that would make the savviest hedgefund investor blush. That's why PE shops are grabbing them up.