Is there any solid reasoning as to why sites shouldn't be developed with ajax functionality that loads major parts of each part (assuming there are elements like the header, navigation etc that remain the same)?

Surely it would be less resource-intensive since the server wouldn't have to serve content that appears on every page, benefiting both the host and end-user.

Answer the question taking into consideration:

• The sites javascript behaviour degrades gracefully in every instance

• For my question I'm talking about new sites where this behaviour could be implemented rather from the off, so it doesn't technically cost any money - we're not returning to a finished product to implement it.