"Dormant Christian" sounds quite positive. I would use the more negative term "vestigial". What you describe is people using the church, or Church, when it suits their need or purpose - like a cultural tradition, or a social club. Church-going, in that sense, served an important social function in the past.
I didn't get married in a church because I don't believe in, or hold to, the words the priest or minister says. I don't want to be a hypocrite. Likewise, I didn't get my children baptised because I don't believe in those sacraments anymore. Again, don't want to be a hypocrite and say or promise things I don't believe in. The only time I'm in churches these days, sadly, is to attend funerals for family and friends.
Many people who participate in these "religious" events don't believe in them. They do it for social reasons. They are "religious" in the most mundane and debased way. They are certainly not Christians. Paying lip-service to a tradition because it's convenient or makes you feel nice and sentimental for a few minutes does not translate into Christian belief or a true religious attitude.