Why is the kaddish titkabel after shacharit on a regular weekday (or indeed any day without musaf e.g. Chanukah), deferred until after (keriat hatorah) ashrei and uva letzion?
One may have expected it to always come after chazarat hashatz (or tachanun or hallel where relevant) as that would seem to be the conclusion of the core shacharit service. This is indeed what we do on Shabbat, Yom Tov, Chol HaMoed and Rosh Chodesh, where it is consistently recited before keriat hatorah.
Does its recitation after uva letzion on a weekday imply that (keriat hatorah) ashrei and uva letzion are viewed as part of the shacharit service?
Conversely, does its location on musaf days imply that keriat hatorah and ashrei (and uva letzion) are not part of shacharit on those days (and maybe even become part of the musaf service)?
(Partly inspired by discussion on this question.)