The main reasons to have insurance is if you should have a problem with your device. These days, it's either a broken screen, or loose charging port. Water damaged devices used to also be a big problem but many of today's devices are water resistant. Unfortunately, not all insurance plans were created equally. Most of the wireless carriers utilize Assurian. About the only good thing I can say about them is they cover lost and stolen devices. Many of these insurance companies offer a $4 service to remotely lock, erase, or find a lost device. Since Apple and Google (Alphabet) offer these service for FREE, there is no sense in paying for this.
Apple also offers their own type of SmartPhone protection. For $129, they extend your 1 year warranty to 2 years. If you have any issues with the device, short of blatant customer abuse, they will normally fix or replace the device for FREE. I've had cracked screens replaced as well as defective logic boards. If there is a downside to AppleCare, it's that they don't cover lost or stolen devices. Of course, you could add the device to your home owners or renters policy. That in my opinion is stupid because most renters and homeowners policies have an $500 deductible. If you had an iPhone 7/32GB device ($650 MSRP) get stolen, you'd still have to pay the first $500. On top of that, your premiums will increase for making the claim.
I personally do not take insurance on my SmartPhones but do put them in carry cases for protection for when the devices gets dropped. For those of you, and you know who you are, that chronically misplace your keys, sunglasses, and SmartPhones, get the Assurian option as it includes loss protection. There are so many great Android devices out there though that if you did lose a high end Smartphone, it could be replaced for under $200, The Motorola Moto G, (Huawei Honor 6), or on the higher end, the latest One Plus 3T for under $500. With the new LG-G6 hitting the market, the LG-G4 and LG-V20 are going to drop in price in the next week or so. Avoid the LG-G5 which was that modular design that sounded great on paper but bombed. Samsung's S7, S7 EDGE and other models will be dropping another $100 each once the new Samsung S8 launches.
As far as iPhone replacement devices, the $399.99 iPhone SE is like a 5s on steroids as it has the same A9 processor and camera as the 6s series. There are also many deals on both new and refurbished iPhone 6 and 6s models at the moment.