Why do we not see much AJAX in secure applications like internet banking?
Ajax can improve usability but adds complexity.
Banks need security.
Complexity is the enemy of security.
- https://www.schneier.com/blog/archives/2018/06/thomas_dullien_.html
- http://www.educause.edu/Resources/SecurityStandardsComplexityIst/162968
- http://portal.acm.org/citation.cfm?id=1218063.1217951
Therefore Ajax is the enemy of Banks ;)
I have a counterexample for you. I'd say mint.com fits into the same category as internet banking sites, and they make heavy use of Ajax. I'd also hazard a guess that their security is better than most banks, but I have no proof of that. The banks just "feel" like they're cobbled together by Highly Paid Consultants, rather than developers who know what they're doing. Mint is a fairly recent startup, and their site design still shows the control the developers have/had.
I'd say the biggest reason is that banks tend to be very technologically conservative/hidebound. It's not uncommon to find a banking site that recommends or even requires using IE6.