safety – Why are lifejackets not provided on some boats?

I’ve been on a few boat trips, and I’ve noticed that lifejackets are not provided for passengers in the event of an emergency on these boats, which sail in waters classed as Category A and B in the UK. To be specific, Category A waters are no deeper than 1.5 metres, and Category B waters are no deeper than 25 metres.

Instead mini life-rafts* and/or life rings (flotation devices) are stored on the boat in a location e.g. on the top of the boat, where they will float freely should the boat sink.

However I can see a number of flaws with this, one being what if an emergency takes place e.g. a fire, which necessitates the evacuation of the boat ASAP but without the floatation devices floating freely, and another being what if they float to a location that people cannot get to them, especially if they are unable to swim, or wearing clothing that makes swimming more difficult, and/or weighs them down e.g. jeans.

Why is it that they do things that way rather than just providing lifejackets for passengers? Especially considering that crew are provided with lifejackets on safety grounds i.e. to keep them afloat should they accidentally fall into the water. On top of that on one occasion I saw lifejackets being stored on a boat, although they were not for passenger use, and the safety instructions explained that.

*Mini life-rafts are not like normal life-rafts, they just have rope on them which you can hold onto to keep yourself afloat, in a similar manner to life rings.