Most forms either don't need any kind of validation or you still have to validate the data on the server and do something reasonable when it fails. Repopulatin

Most forms either don't need any kind of validation or you still have to validate the data on the server and do something reasonable when it fails. Repopulating the form on the server side after validation failure is trivial and even more so when there are libraries that abstract that away (eg. wtforms). On a similar note I somehow fail to see the benefit of writing (and often duplicating) large parts of business logic in client-side javascript and replacing perfectly good HTML form-submission mechanism with random JSON "REST" APIs.