In Berakhot 32b, Tosafot (s.v. קודם תפילתו) provide a reason as to why we start Ashrei with Psalm 84:5. In their words, it's "לאפוקי מנהו דאמרי אשרי הרבה", which either means to exclude or to exempt those who recite Ashrei many times (or those who recite many ashreis). Excluding somebody can denote marginalising them; exempting somebody can also denote allowing them to carry out a practice - like יצא in Hebrew.
What are they referring to? To put this into historical context, the tosafot recorded in this tractate are those produced in the school of Evreux, which Wikipedia tells me flourished at the beginning of the 13th century. Do we know of any customs around the recitation of Ashrei from this time? People who said it repeatedly, or who said many different varieties? And what do Tosafot think of this practice? Are they for it or against?