At least some companies building on Nostr are already considering how users can be monetized, and I recall at least one mentioning introducing advertising at some point (Plebstr team). Whether and how to use user data such as likes to determine user behavior and preferences and whether and how to incorporate advertising is inevitable for any company as they grow. Any user data can be used to feed algos, etc, but my issue with likes specifically is the lack of cost to produce them and therefore their real value is as mechanism to inform companies/advertisers, not to provide meaningful interactions between users.