Doesn't mean that people are more fountain pen minded later in life.
Yesterday I lent my pen to the server in the restaurant (her ballpoint ran out), and she told me that she had not used a fountain pen since her school days.
My kids are converted to cheap rolleballs and felt pens as well, despite the fact that both had a quality fountain pen in school.
Perhaps, but many people tend to stick with what they know and with what they grew up doing.
I would also think that the fact that modern fountain pens are a lot cleaner, leak less, and are less of a hassle than older ones probably has a bit to do with it.