Back in the day, most AFIZ were at aerodromes that were predominantly origins, destinations, or waypoints which tended to concentrate the traffic. That's why they were established. There wasn't a whole lot of passing nearby traffic. As pointed out, most aircraft when they called inbound were only 5-8 minutes out, a jet maybe 3-4. Didn't seem an inordinate or troublesome impost, especially when straight in approaches got the nod. If you are going to have someone assess and pass traffic, weather and other relevant info, you have to give them time to do it. In most cases it was done far enough out for the pilot to then be able to concentrate on their approach and landing.
Why is it huge? To catch lots of aircraft to make it look busy?
If they are all coming from or going to the same place, it doesn't matter how big it is. You're not catching any more aircraft.