I believe using the timing belt or timing chain is really an attitude issue by the car manufactures. Rubber belt, not like the metal chain, is hard to predict its life. Do you need a new belt when your Honda RDX is 8 years old but has only 60K miles? As we all know, like tires, life of timing belt is affected by the age in addition to the usage. If you have timing chain, this is a non issue. Timing chain can also be designed to last for the lifetime of your engine as they both are made of metals. Even if you have issues, it won't break suddenly like timing belt. You have time to react and fix it, whereas on timing-belt equipped engines, this sudden break will be disastrous as all engines are now interference engines. Timing belt was used mainly on OHC engines in the early days when the engine is non-interference, hence if the belt breaks, it doesn't matter. When engines became interference, timing belt should be obsolete.
Honda normally has reliable timing belt system if you do the replacement by the book. But I've still heard some incident of breaking earlier than specified schedule. And some owners simply just ignore the maintenance until the disaster happens as there is no symptom or noise before belt breaks. If you own certain brands such as VW or Audi, the timing belt has been breaking earlier than scheduled 105,000 miles more frequently. And many owners found out the replacement schedule might have to be 60,000 miles according to the factory sticker inside of engine bay!
As the necessity of water pump replacement when you're replacing the timing belt, that's because the water pump is driving by timing belt. If pump breaks, it causes chain reaction to break the timing belt, bend many valves and may even damage the positions. Hence people replace the water pump when they replace the timing belt, and all components timing belt touches! But if your car has a timing chain, none of above worries exists! Timing chain system is almost like a fail-safe design unless the chain itself breaks suddenly which is highly unlikely. Water pump will be driven by serpentine belt which is easy to replace if it ever fails, and it won't cause a chain-reaction and become a catastrophic disaster. Yeah, timing chain system doesn't immune to problems, especially the plastic tentioner used by many car manufactures with now watery thin oil in the name of fuel economy. But if you change oil regularly, a timing chain system rarely has issues and needs any attentions. I've heard many Nissan cars which switched to timing chain in early days and accumulated over 200K miles without any issues. As I mentioned, Honda is the only car manufacture insists of using the timing belt on its V6 even though all other car manufactures, even very conservative US automakers, have switched. They all can see the benefits of using timing chain with little extra added cost, but not Honda.
This is simply an attitude issue. Honda believes using the timing belt on its V6 is fine even though it's not a fail-safe design and requires routine expensive and unnecessary maintenance. Honda did switch belt to chain on its I4's. But for some uncharacteristic reasons by Honda, they simply just refuse to do the same on its V6's. On the other hand, they spent money on an illogic and problematic cylinder-deactivation VCM system to save little MPG on the highway which is now having problems and causing class-action lawsuit.
