One must also not forget that when it comes to species like reptiles, amphibians and fishes there are also some practical limitations. It's quite expensive and complex to develop facilities to properly take care off and breed those species. Especially single-of exhibits are quite difficult.
For example aquarium filtration is cheaper and easier to have for an entire aquatic building then for a number of aquaria spread throughout the zoo. Things like live-feed cultures, reverse-osmosis water plants, automatic water mixing systems (either with salts, chemicals or with pure water) are especially more expensive and difficult to have all over the place. You could use a central hub, but these things are also easily taken care of in between things and transporting large amounts of prepared water is also very impractical.
For reptiles, you have incubators, breeding rooms, rearing terraria, live-feed storage etc. that's also best placed together, and the further away your terraria are from these facilities the more difficult it is to maintain them. Walking between spots also takes a lot of time, so either you have reptile keepers losing a lot of time on moving between exhibits or you have keepers taking care of different groups of animals. However those last ones have a will rarely develop in the experts you need to breed many reptiles and amphibians.
Edit. note that this is less of a problem in zoos with a taxonomical presentation, but more a problem for zoos working in larger geographical or habitat-based themes.
For example aquarium filtration is cheaper and easier to have for an entire aquatic building then for a number of aquaria spread throughout the zoo. Things like live-feed cultures, reverse-osmosis water plants, automatic water mixing systems (either with salts, chemicals or with pure water) are especially more expensive and difficult to have all over the place. You could use a central hub, but these things are also easily taken care of in between things and transporting large amounts of prepared water is also very impractical.
For reptiles, you have incubators, breeding rooms, rearing terraria, live-feed storage etc. that's also best placed together, and the further away your terraria are from these facilities the more difficult it is to maintain them. Walking between spots also takes a lot of time, so either you have reptile keepers losing a lot of time on moving between exhibits or you have keepers taking care of different groups of animals. However those last ones have a will rarely develop in the experts you need to breed many reptiles and amphibians.
Edit. note that this is less of a problem in zoos with a taxonomical presentation, but more a problem for zoos working in larger geographical or habitat-based themes.