Why don't js load on simple landing pages for some users? Is it global?

Question

JavaScript

There is a landing page with a form to fill out, which is submitted using js in a file. Analytics show that 10 percent of login pages are not / , but /?name=Alexander&phone=709496864645 . That is, js does not work to process the form, but it submits by default, reloading the page and passing parameters as in a get request.
What are the common reasons why js is not loading for some? I don't think that someone disables js... Or maybe it's common in mobile browsers?

Answer 1

Some turn off, but hardly 10%. Rather, the reason is that the scripts are not quite cross-browser, and fall off somewhere due to an error. Look in the user agent logs, you might find a pattern.