Saggi You clearly do not live in a flood zone. Flooding can be very localised and sudden. Likewise blizzards, and very high winds.
Weather forecasts are vague and unreliable and my experience is that the BBC is a lot more unreliable than most.
You are also assuming everyone has smart phones. I have dyspraxia - and a smart phone, but dyspraxia makes it difficult for me to make use of the facilties smart phone offers. I have problems with sequencing, plus difficulty using those very tiny symbols. Not helped by being right handed and having 3 fingers of my right hand where the finger tips are numb
The whole point of alerts is that they warn of a near and present danger, and are not vague warnings about heatwaves due this week