From time to time I am asked by couples to officiate at a wedding scheduled during the intermediate days of Passover. I explain that the Jewish tradition, as a rule, insists that joyous occasions not overlap. Since Passover itself is a joyous occasion, weddings are not celebrated at the same time. Perhaps, on some unconscious level, Jewish law reflects the notion that spreading joy over a wider time frame is preferred to concentrating joy in a narrower time frame. Increasing celebratory occasions is the proper response to a history dotted with tragedy.
To at least one medieval source, the principle that "we do not mix one celebration with another" comes to explain a textual difficulty as well. The Torah (Leviticus 23) teaches that the period of the Omer from Passover to Shavu'ot is counted from the second day of Passover. But why? It would seem entirely reasonable to begin the count from the onset of the Passover festival rather than after the first day!