CPA Lars got rich uncle Nils's real estate into family partnerships in the early days of that device's popularity. Being in the financial business with a lot of wealthy clients, Lars got exposed to the advantages. Even the early limited partnerships offered asset protection, at least for those limited partners who weren't also the general partner. When limited liability companies were authorized they offered even the general partner (now to be called the manager) a shield. Lars has helped Nils to convert his LPs to LLCs with little cost or tax effect.
LLCs also offer a good way of making gifts to save estate taxes. The founder is usually a manager, and can keep control of the investment despite having given away shares of ownership. Part of the appeal is in the valuation of the gifts. A 5% interest in an LLC with a $2 million building would seem to be worth $100,000. But you couldn't sell it for that, because a new 5% owner would have little control over the fate of his investment, and a scant market for unloading it. So an appraiser might say it's a $70,000 gift, thus saving $30,000 of the donor's gift tax exemption. Some call this a "discount," but it's just the reality of the value of the interest given.