Final answer:
Advertising on brand keywords can be ineffective due to firmly established brand names and the abundance of advertising messages on various sources and platforms.
Step-by-step explanation:
Advertising on brand keywords can sometimes be ineffective.
One reason for this is that a firmly established brand name can be difficult to dislodge due to large advertising budgets. In addition, advertising messages can be received from a variety of sources and platforms, making it difficult for advertising on brand keywords to stand out.