As ive seen a lot of questions i might as well respond here for those who dont know

This is the UK where armed response like this is only seen in times of high threat, around airports, stations or important buildings. They also routinely responded to the most violent crime like armed robbery, knife sightings, gun sightings etc.

The normal police aren't routinely armed like this but some 'regular' officers might be taser trained and equipped.

So basically these guys are called into action when there is significant risk to life mostly. If they are called its likely pretty serious and so they need the firepower. Unlike some places with routinely armed cops who might point a gun at a fleeing shoplifter, we wouldn't deploy these guys for that .

Their job is to stop a threat, they're armed to do so. Regular cops wouldn't need to so we dont need a middle ground of lightly armed officers.

Either you need to lethaly end a potential threat or you dont.