I think that the reason why they would want a prominent unit is because it is a prominent unit!
To Deano: I think that your views have merit but consider this - most shopping areas do not operate on purely market forces. I think that most town planners worldwide recognise that this is not desirable.
What this is about, IMHO, is not Dominos per se, it is an issue of zoning and how a business operates. The current site is zoned to be a restaurant with arguably very good reasons and there are some very persuasive arguments as to why a takeaway delivery is not suitable there too - see posts passim which will lead you to objection letters that outline this. The Forest Hill Society letter is a very good starting point.
Also, to really stimulate the market, one requires a safe environment that encourages people to shop and visit. If the most prominent shopping unit isn't really a shop, more of a delivery hub, then this isn't much of a stimulus is it? No more so than a empty unit, I'll grant you, but is that progress?