Some married people are still spiritual, but it’s unusual.
To give them the benefit of the doubt, it should be explained that married people, especially older ones, are generally not trying to work on being more spiritual because:
1. they naturally lose the energy, fire, and idealism of youth;
2. spirituality is about growing and changing, and older people typically become set in their ways (“balabatish”);
3. married people spend most of their time thinking (legitimately!) about discharging their material responsibilities and simply have very little time for sublime pursuits;
4. they may be challenged by various sources of distress (may it not befall us) that distract them from pursuing their relationship with Hashem.
According to the Gemara in Taanis 5b, this is the meaning of the words of Dovid HaMelech (Tehillim in the Shema Koleinu prayer of Selichos: “al tashlicheinu le’eis ziknah”—“do not cast us away to old age,” not in old age. The Gemara says that this pasuk is saying that while we are young, we should not lose the energy of youth and become old before our time. It should be noted that this is one of four phrases that we open up the Aron Kodesh to read, this point is clearly regarded as the climax of the service. This demonstrates the importance of this request.
Moreover, what is wrong with old age? And why do young and old put forward the same request? Obviously one can be young on the calendar but lack the passion of youth, or old but still feel “young at heart.” As chassidim say, “the years don’t go according to the passport” (sicha to Machaneh Yisrael, Tishrei 5740s). We ask in Selichos that whether we are young or old, we should be able to maintain this spiritual vivacity, so we can always serve Hashem at our peak.