People get lost or stranded everywhere, not just up mountains or out in remote wilderness. Cars crash into ravines or dense bush, people wander off from the beach or are trapped by the tide, trampers become lost or injured on a simple day walk, the examples are almost endless.

Search and Rescue technology has improved greatly over the years.
But in difficult terrain and weather, success still often comes down to teams out searching on the ground.

There are many options available but none are considered ideal in many circumstances:

EPIRB / ELT Locator Beacons
…need a good view of the sky to activate Satellite Network and for any onboard GPS device, can be expensive and are not used by motorists, anglers and people on short walks

Satellite Phones
…need a clear view of the majority of the sky, can be expensive to buy and operate and are often only used by those who are frequently out of normal cell phone network coverage

HF Radio
…unfamiliar to many and must be purchased / leased with service

Avalanche Beacons
...very specialist application and have a very specific use only

Audio Visual Methods
…includes whistles, torches, flares, heliographs. All have limited ranges and capabilities

In short, most solutions are specialised and have limited uptake by the public