Maybe, MSO. But, if they smoke cigarettes 99.9% of the rest of the time, and only smoke a pipe a few times a year, then are they serious still? Or, if someone smokes five cigars a day and dips between them, and then smokes a bowl of Prince Albert on Sundays, then are very serious?
Anyone who picks up a pipe and starts to smoke it, whether it is their first time or not is a pipesmoker, at least for the duration of the bowl. So, I think one can be a pipesmoker without having to dedicate too much thought to it.
And, my neighbor friend whom smoke one pipe and has only ever smoked Prince Albert in it, but smokes it all day long has never been seen without his pipe. In fact if someone wanted to refer to him in conversation he would be known town-wide as, "the angry guy with the pipe." If that's not serious, then I have no idea what you are talking about.
Then we have fanatical levels of pipesmokers that have collected the most pipes or amassed the most tobaccos. Sure, they are serious, but probably beyond.
To me it just makes more sense to say that someone who makes the pipe their preferred means of smoking tobacco is then a serious pipesmoker. All other indicators of pipe fanaticism is merely dick swinging to make themselves look more serious that someone else.