What are the reasons NOT to invest in syndications?

If real estate syndications are so great, why isn't everyone piling into them? Let's be honest: it's a pretty small niche of the investing universe. So there must be good reasons why other people are not jumping in to syndications with both feet.

Here are a few guesses--let us know if you have more ideas:

Lack of information and knowledge about syndications: we suspect that may people simply haven't heard of syndications. At least in some cases, these syndication deals can't be broadly advertised easily in the same way as other kinds of investments and those offering the deals do not have the same marketing budgets as those marketing other kinds of investments. Think about all those ads you see for CDs that banks offer, for instance. Most investors know about CDs and the rates they can obtain. The banks involved have huge marketing budgets and few constraints on how and when they can market the deals.
What we've been told and sold by the investment industry (aka Wall Street): We've been conditioned to consider simpler types of investments: publicly traded stocks, bonds, and cash. We've all heard the advice: "Invest in your 401(k) or 403(b) and use target date funds and so forth." We do that too. You might even have bought into a single family home or small duplex to rent out one or more apartments. But these types of syndicated investments are sometimes called "alternative" investments. They have historically been thought of as limited in access--a "country club" type investment just available to those who have special connections to other rich people. The advent of the Internet, crowd-funding, and changes to the regulatory environment have made these deals available to a much broader set of people--at least, available to accredited investors. Other deals, via crowdfunding sites, are available to any investor.
Lack of control: Let's assume you've learned about syndications via this site or otherwise. What might hold you back on the merits?
Illiquidity: You have to tie up your money for 3, 5, 7, 10 years or more. You have no way to get your money out of some deals before the syndicator says you can. Read the Private Placement Memorandum (PPM) with care to understand the circumstances under which you can get any money out of the deal. It may be you cannot get a thing out of the deal for years. You should, of course, get paid for this illiquidity. But in the meantime, best if you don't need the cash.
Hard to choose a syndicator: We know--it can be hard to get started, to build a network, to know which syndicator / sponsor / operator to go with. That takes time and relationships. And a lot turns on this choice. Vetting them in a way that you feel comfortable about can be a challenge.
Hard to choose a deal or fund: Even once you've selected a syndicator, which of their deals should you invest in? And when they roll out a fund--in which you don't even know the investments exactly that they will make--should you jump for that?
Complexity: These deals are complex. There are often hidden terms in the agreements that can trip you up.
High minimums: Most real estate syndications these days look for $50,000 to $100,000 as a minimum. Some have lower minimums ($25,000) and we've seen some good ones with higher minimums too ($250,000). Those can be major hurdles for many investors. As with a house down payment, you may have to save up for a while to be able to invest in one.
Fees: The costs can be very high compared to other investments. One fund we saw recently had a 65/35 split: that means that you get 65% of the profits and the people running the fund get 35%. And that doesn't account for various other fees that you will pay along the way with each transaction. Even the hedge fund industry might balk at those prices (ever hear of "2 and 20"? That means that hedge funds often give you an 80 / 20 split in addition to their 2% management fees. Fees in this field can cover acquisition costs, management costs, disposition costs, and more.
Risks: These are relatively high risk, high reward deals. Pro formas will show you plans to "double your money in 5 years" on an overall return basis. That possible reward comes with high risk: maybe the operator doesn't know what she/he is doing and needs more capital (via a capital call) from you to complete the business plan. The risks and rewards are both real.

A way to get started is via the crowdsourcing sites, such as Fundrise and Crowd Street, which offer lower minimums typically and pre-selected deals. It's a way to dip your toes in the water of private real estate investing while you consider whether a larger commitment to a syndication could be for you.