Apple is not “required” to enforce its mark in every instance or risk losing it. The circumstances under which a company could actually lose a trademark—such as abandonment and genericide—are quite limited. Genericide occurs when a trademark becomes the standard term for a type of good (‘zipper’ and ‘escalator’ being two famous examples). This is very rare and would not be a problem for Apple unless people start saying “Apple” simply to mean “smart device.” Courts also set a very high bar to show abandonment (usually years of total non-use). Importantly, failure to enforce a mark against every potential infringer does not show abandonment

[1] https://www.eff.org/deeplinks/2013/11/trademark-law-does-not...