In this case "left to fend for themselves" manifests as "users end up with a non-working (on some sites) browser, switch browsers". So it's not really an optio

In this case "left to fend for themselves" manifests as "users end up with a non-working (on some sites) browser, switch browsers". So it's not really an option, unless the browser involved is a monopoly and the site involved has a tiny audience.