You can lose your trademark protection if the term becomes genericized and you fail to police its use. It's exceedingly rare for this to happen, the law isn't clear-cut, and different courts have ruled differently in similar cases, but it is technically possible. Velcro doesn't have to rabidly attack everyone trying to genericize its brand, and so long as they are still using it themselves and making some occasional effort to legally defend it, they're fine. But if other brands started calling their products "velcro" in the generic sense, and Velcro ignored it for a decade or more, they could in fact lose the trademark entirely.
You can lose your trademark protection if the term becomes genericized and you fail to police its use. It's exceedingly rare for this to happen, the law isn't clear-cut, and different courts have ruled differently in similar cases, but it is technically possible. Velcro doesn't have to rabidly attack everyone trying to genericize its brand, and so long as they are still using it themselves and making some occasional effort to legally defend it, they're fine. But if other brands started calling their products "velcro" in the generic sense, and Velcro ignored it for a decade or more, they could in fact lose the trademark entirely.
Edit: https://en.wikipedia.org/wiki/List_of_generic_and_genericize...