Part of the idea of large outworlds being a detriment just comes from the idea that they are unnecessary for the vast majority of species/colonies. For a small colony especially, if food is placed extremely far away in the outworld, the ants may never come across it, or if they do it will require much more energy to be expended for round-trips to that food source. Social stomachs aren't indefinitely big, so more often than not round-trips are necessary to extract enough nutrients from a food source, and if a colony is needing to travel a much further distance, that is an energy cost that may be noticeable, especially in a small colony.
There is also the issue of space: not everybody lives in a mansion, and many antkeepers are young people restricted to a small space. Unless you only have a few colonies, it's quite difficult to provide every colony with all the space they could ever want.
Lastly, as someone that sells antkeeping supplies, I can say that outworlds are costly to both manufacture and ship. Making a professional-looking outworld that is large and cheap is simply not possible. It's easy for an antkeeper to buy a large storage bin from Walmart and use that, but a business selling professional setups just can't do that. That's why (at the moment) all of the nests on arthropodantics.com are sold separately from outworlds, so that if my customers would rather create an outworld by themselves to serve them and their colony's needs, available space, and budget, they can do so. At the same time, I have gotten complaints for this, as some people prefer the convenience of their nests including an outworld out of the box, so that the setup is ready without needing to connect anything else. This is part of why I'm working on developing an all-in-one nest right now.
Trust me, I am a believer in large outworlds; anybody who's seen my Pheidole rhea's setup and their 55 gallon outworld will be able to tell you that. Part of the reason I opted to make that large outworld though is because the species are extremely avid foragers, creating trails that are literally hundreds of feet long in the wild. Well, that and the fact that they are my dream species; of course I'm going to go a bit crazy on their setup, lol. It's just also worth noting that large outworlds not only can be detrimental, but also are just unrealistic for the majority of antkeepers and ant supply companies to provide/use.
