In the early days of the Web—around 1995—form controls were added to HTML in the HTML 2 specification. Due to the complexity of form widgets, implementors chose to rely on the underlying operating system to manage and render them.
A few years later CSS was created, and what was a technical necessity, that is, using native widgets to implement form controls, became a style requirement. In the early days of CSS, styling form controls wasn’t a priority.
Because users are accustomed to the visual appearance of their respective platforms, browser vendors are reluctant to make form controls stylable; and to this day it is still extremely difficult to rebuild all the controls to make them stylable.
Even today, not a single browser fully implements CSS 2.1. Over time, however, browser vendors have improved their support of CSS for form elements, and even though there’s a bad reputation for its usability, you can now use CSS to style HTML forms.
