2 motivated CE HoFs produce 3500 Guild Power per week.
That's a lot more Guild Power then I produce fighting 64 in GE.
That;s the same as holding 3 of the best Sectors on the CE GvG map every day.
I've run 23 HoFs in my main city for about a year. They produce around 6000 Guild Power per day. Call it 2 Million Guild Power over that year. That's about the same as holding 25 or so CE GVG Sectors every day for a year.
I suppose I could build something else in my city in all that space, but I don't see anything that my city needs.
Cpntrariwise, HoFs are pretty useless until a player gets up to Modern or so. The space they take up can be used much more profitably to advance the city,