Hey,
anytime. No biggie. Don't worry about it. Psycholinguistic research
reveals that we choose our gratitude acknowledgements pragmatically,
proving that such language isn't phatic (devoid of content) after all.
University of Western Ontario psychologist Albert Katz suggests men, in
particular, may use "anytime" to convey dominance by signaling they
have sufficient means to do the favor again in the future.

In
a study, people responded to written scenarios that described them
doing someone a favor. Manipulating the "cost" of favors in terms of
time, effort, or money, Katz and two colleagues asked the volunteers to
choose responses to thanks and justify their choices. Not surprisingly,
open-ended phrases like "anytime" and "whatever you need" were used
less when favors were costly.

But there was
also this surprising finding: When men used "anytime"—and
explained their choice as an invitation to be asked to perform the
favor again—it was far more often for high-cost favors and when
the favor-asker was male. Katz speculates that the men were displaying
"a linguistic form of alpha-male behavior," in other words saying, "
'Hey, I'm higher than you in the dominance hierarchy—I have the
resources.' " —Conrad McCallum