Well they're not offering it yet... most brokerages are busy scrambling to add robo-advisor-like services to their platforms to capture the millennial crowd who weren't really investing their capital before. I met one person who had hundreds of thousands of dollars... in their savings account! There's definitely a lot of capital to be captured there.
At the same time, many companies are staying private longer. Their accessing private capital from a growing number of accredited investors and the SEC is still trying to figure out how to let them raise private capital from unaccredited investors. Just look at the size and quantity of these HUGE private companies and compare that to historical norms. The companies going public today are much closer to breakeven when they IPO and are IPO'ing mostly for the exit vs. the raise. DocuSign is a great example, they filed an S-1, talked to some folks, then pulled the S-1 and raised $200M for their growth.
Similarly, there is an incredible growth in private real estate transactions under the crowdfunding banner. People are leaving the public markets in search of alpha and/or income producing investments and brokers are losing out.
The only logical conclusion is that once the regulatory risk of managing accredited/unaccredited status has died down, brokers (I predict TD will be the first) will add the ability to connect with private markets. The question is will this be more of a partnership with platforms like AngelList where the AL managed syndicates are listed at a broker or will brokers attempt to take on company by company investments themselves? I predict the former as the complications are reduced and from a fiduciary perspective these fund of funds are likely to carry less risk (and likely a little less return).
Btw, if you want pre-release content from my book on angel investing sign-up here.