Oscarh and 6-Dof.
There is a popular misconception that lifejackets and rafts are only there to give passengers a false sense of security because it is often assumed (wrongly) that when the plane goes down, there will be no survivors.
I usually sit in the front with the big windows, but often I am a passenger positioning or travelling on holiday. Many passengers ignore the safety brief and this reflects the excellent safety record of air travel. However, take it from me that if an aircraft does have a serious emergency over the water, then all those items of equipment may be the best chance anyone has of seeing their next birthday.
Yes, the ditching 767 off the Comoros islands did break up, but there were still 57 survivors. There would have been even more if the pilots had been able to keep the wings level and make a controlled ditching - unfortunately they were unable due to the actions of the hijacker/s.
I have sometimes thought about the what ifs when flying over the pond or the Indian Ocean. Imagine a fire in the cabin when you are a couple of hours from a place to land. The cabin crew will fight the fire but if it gets out of control, the next best thing may be to put the aircraft down on the water before losing control. I am confident that there would be many survivors. All would survive would be my aim.
Once out of the aircraft, the first concern would be not drowning, hence the lifejacket. The next would be hypothermia. Getting out of the water into a liferaft would be the priority for this, and for subsequent detection and rescue by any ships in the area which would already have been alerted following distress calls from the aircraft.
Shorthaul aircraft may only carry lifejackets, the idea being that survivors in the water would be fairly close to rescue opportunities.
It's all a matter of risk assessment. I want to emphasise that the risk is extremely low. However, if it's not your day, then all is not lost in a scenario such as the one described.
To get back on line with the thread, low life who steal safety equipment are putting others at greater risk. It would be like removing the airbag from your car. These people should be appropriately dealt with. Not much chance of that in UK, they will probably be offered councelling!