The purpose of the CBP Trusted Traveler programs is to establish that you are a low security risk. They want to know about any criminal history, associations with terrorist or anti-government groups, violations of customs or immigration laws, and so on. To help with that, you provide them a travel history they can look over for suspicious destinations.
Your non-travel to a non-suspicious destination is not going to constitute a reason for denial. Consider furthermore that they don't expect you to know your exact travel plans for the next five years. Someone applying for a NEXUS card because of frequent work travel to Canada might switch jobs and no longer make those drives; that alone is not going to cause either the Canadian or American government to decide that she is now a threat.
The application form does not ask any questions about when or where or how you plan to use the program. You are not required to make any number of trips to any particular destination over the lifetime of the membership to maintain it, either. It's not unlike someone applying for a passport but never going on any international trips. In fact, it's less strange than that. The NEXUS processing fee is subsidized expressly to encourage people to apply for it, and it's not against the law to take advantage of a bargain even if you're interested in some benefits more than others.
If you are asked about it during the interview, just be truthful. I doubt you will be asked, however. If you're like me— a natural-born U.S. citizen with a clean criminal record and no ties or past travel to suspect countries— the interview is something of a bureaucratic formality; they've already done the background check at that point. My Global Entry interview lasted at best 10 minutes, and the vast majority of that was the interviewer reading from a script and then taking my fingerprints.