Remove admin bar for subscribers

I did a quick research on this and I don’t think you can with a function, as said in the codex.

Note: It is no longer possible to hide the Toolbar when viewing the Administration Screens, but users can disable it on the front-end of the site in their Profile screen.

Disabling in the frontend results in the same as you’ve already done.

I would suggest hiding it with css.

#wpadminbar {
    display: none;
}
html {
    padding-top: 0; // Move up the page's content by the bar's height
}