What are the scenarios where you know the 3 words but not the lat-long?
The only justification is the ease of communication over the phone.
I only don't like that it's proprietary and the company responsible is pretty aggressive about enforcing their rights - there shouldn't be a place for that in public emergency services.
I mean.. as opposed to two numbers? A slow speed high error correction audio encoding of them would be easy. Call emergency services, press the button, they decode the tones, immediate, accurate, simple.
If you mixed the calling and playback into a single action, you could make calls and direct people without even the ability to speak.
Maybe it helps with an issue they have noticed with certain callers that I'm not aware of.
At least wiki brightened my mood : The site has been parodied by others who have created services including What3Emojis[29] using emojis, What3Birds[30] using British birds, What3fucks[31] using swear words and What3Numbers[32] using OpenStreetMap tile identifiers.
In situation A, it's going to be a lot quicker and clearer to communicate w3w than an ll pair (for the same precision a ll pair requires 12-18 digits, plus specificity on +/-).
In situation B it's going to be a lot easier to remember the w3w descriptor, and you still have the same advantage as in situation A.
For spoken communication, w3w's rival is "it's 123 Fake Street, I'm the bloke in the green parka", not ll pairs.