On the one hand, who applies for a job if they don’t want it? On the other hand, applying electronically has made it possible for people to apply for tons of things they would not have traditionally spent the money to photocopy a resumé and pay the postage for. So, yeah, people DO apply for things they aren’t particularly interested in, and I can see where a recruiter would like some sign to differentiate the truly interested from the I-just-happened-to-be-in-the-neighbourhood types. On yet the oher hand, you can also imagine people getting skilled in feigning interest, even when waiting to hear about something else they want more.
So, it’s not always “forward”, but then neither is it always sincere or diagnostic to the recruiter.
My gut says, play it by ear.