Quoting Ben Hutchings <b...@decadent.org.uk>:
Many of the rules in Debian policy are there to support a minority of users, but we try to follow them anyway.
Hear, hear! I was about to write the same thing. I personally don't care about usrmerge, but if it is useful to a relevant minority, we should not reject it. I'm so thankful, that Debian took the hard and rocky road of MultiArch, which is probably not needed by most users. But it is incredibly valuable to me. Same thing for support of e.g. armel and armhf, which makes my life significantly less miserable.