There may be several reasons. One reason is of course that the Y2038 event seems so far off. Being over 20 years away, there is no sense of immediate urgency to fix anything. However, this is the same type of thinking that was partly responsible for the creation of the Y2038 issue to begin with.
Another reason you may not have heard about Y2038 is probably due to the extensive media coverage that preceded Y2K. Perhaps in part due to the heightened awareness by mainstream media, the Y2K issue was almost fully mitigated prior to Jan 1, 2000. When Jan. 1, 2000 arrived, there were no catastrophes, and there was a public sense that the Y2K event had been over-hyped. In fact, it is likely that the extensive Y2K media coverage forced businesses to thoroughly and proactively address it. (Chances are, media coverage will similarly increase before 2038).
Yet another reason may be a general lack of understanding of Y2038. Y2K was fairly easy to understand, but Y2038 requires a deeper understanding about the digital representation of time in computers.