This is particularly true for Souther Baptists. About a quarter of all nondoms are affiliated with the Southern Baptist Convention, yet claim no denomination so are not counted as SB.
Recently there has been a rush to remove Baptist from the names of churches in an effort to attract more people. Especially in areas outside of the South where the words Baptist or Southern Baptist carries negative connotations. About half of these churches not only remove the name but change the affiliation to nondenominational while in essence remaining SB.
I can only speak from personal experience, here in the Midwest (Kansas) the people whom I met in the NonDoms were of various backgrounds that came out of the traditional denominations because of the attitude of the leadership towards being spirit filled. I remember going to a precious church all black called Mount Zion Baptist Church, the first lament out of the pastors mouth was that they were Baptist and they were spirit filled and that they were staying spirit filled no matter what the head office had to say. I knew Catholics, Methodist, Nazarenes, and many more who had left the denominations because of their stance on the in filling of the Holy Spirit. I do not know what the attitude is today with the denominations concerning the infilling so I can not speak for or against that fact.