Before my wife and I were married, we underwent the obligatory meetings with the Pastor who would perform our ceremony to discuss our wishes for the wedding, as well as other issues. When it came to the issue of music, we worked with the church's music director, a fine organist and musician who had a wealth of suggestions to make as to what to use for the Processional, the hymns, the Postlude, and so on. The only rule we were asked to observe, with respect to music, was that we could only select music that was religiously themed -- i.e., no pop tunes. We were only too happy to observe this stipulation; it never occurred to us to use some popular song for our wedding. However, this is not the case for everyone; at a wedding we attended two years later, "My Heart Will Go On" was given a central position smack dab in the middle of the ceremony.
Well, it's not just weddings that are being popularized these days. According to this NPR story, in the United Kingdom popular music is turning up more and more at funerals. Wow. There is even a Top Ten of songs used most often at funerals. I won't reprint the Top Ten here -- it can be read at the link above -- but I will say that it's an interesting list. (And that "My Heart Will Go On" is on it.)