The only reason to buy one is as insurance against outliving your cash.
Well, not the
only reason, but it's the general one. Here are some rare exceptions to that generalization, in no particular order:
1. For tax reasons in certain countries, such as with "charitable remainder trusts" (CRTs). For example, if you want to donate a substantial amount to a U.S. university, and if you are a U.S. person, you can donate in-kind assets in a CRT arrangement. You receive an income stream, for life (and joint/survivor if you like), and you enjoy lots of tax savings. The university gets a donation -- and also might name a building or professorship in your honor. Twenty-five year old Silicon Valley titans can do this and occasionally have.
2. As another example of tax motivations, if you're receiving a big windfall that would be substantially taxed in the highest tax brackets, the tax authorities might let you receive that windfall in the form of an annuity, to drop you down into lower tax brackets on that income. That's called "income smoothing," or at least that's what I call it.
3. In certain divorce settlements, including some with pre-nuptual agreements, there might be a requirement to set up a lifetime annuity as part of the settlement.
4. More generally than divorces, if for some reason you don't have full confidence that the recipient will manage his/her finances well, you can set up a lifetime annuity. (See "trust fund baby" or "trust fund child" for the basic idea.)
5. Corporations will sometimes buy annuities for top executives, for a variety of reasons including tax optimization, retention objectives (e.g. with escalating vesting), for ex-executive "expenses" (secretarial assistance, for example), and to keep former executives "on side" for life. (The continued payment of the annuity might be contingent on the executive not commenting on the company and otherwise not interfering with the company.)
6. Some universities, particularly public university systems, offer pre-paid tuition plans, arguably a type of fixed term annuity. Let's suppose you have a newborn (or newborn grandchild), and you're concerned about escalating tuition and other university education costs. In these programs usually you pay the current tuition rate for a 4 year degree, up front, and lock in that price. (Sometimes with a discount.) Your child/grandchild will then be able to attend that university, or university within that public system, without any additional payment. (Some of these prepaid programs even have a prepaid room and board option.) And, if the child doesn't attend that particular university or system, the funds can be spent elsewhere or retrieved, albeit with a mediocre return (usually).
7. Royalty, long-term leasing (such as mineral rights), and patent licensing arrangements might sometimes require purchase of fixed term annuities.
8. People and organizations doing business with poor credit risk people/organizations might require purchase of an annuity.
9. Annuities are useful in certain jurisdictions for asset protection reasons. One of the interesting aspects of CPF, including CPF LIFE, is that it's well protected against most judgements and creditors, worldwide.
10. Lottery winnings are often paid out in fixed term annuities, occasionally lifetime annuities. The basic reason is that the lottery promoter can advertise a compelling "$1 Million Prize" with lots of exclamation points then, in the fine print, disclose that the winner actually receives $25,000/year for 40 years.
11. Sometimes purchasing an annuity makes sense as a currency hedge, at least in part.
12. For the care and upkeep of pets, burial sites, cryogenically preserved body parts (or whole bodies), gametes, embryos, surviving domestic workers, girlfriends, boyfriends, memorials, flags, libraries, scholarships, etc., etc. In these cases the annuity payout is often perpetual.
....Anyway, none of these fairly exotic exceptions apply in this case, I assume.
Fun Fact: The Dutch government is still paying interest on perpetual bonds (a.k.a. consols) that were issued in the early 1600s. Yale University is holding one of those bonds, issued in 1648, and is receiving interest payments. These are government issued perpetual annuities. The Dutch government issued them to fund (what else?) construction of dikes, canals, and other water management-related infrastructure.