Adding this method would be helpful for everyone.
As also specified by Darryl, disabled controls are not passed to the controller via the viewmodel. Consequently having a method directly via razor to specify readonly would be perfect.

Also, it's not even possible to use a static class extension because the HtmlAttributes are cleared when the standard HtmlAttributes function is called. (See request 1 and 2, and an example stackoverflow)

Only having 'disabled' is insufficient.

Disabled fields do not post with the form.

Please add ReadOnly properties to these controls