This will be key for bulk actions being built for User Overview and Segments (in beta) improvements. 

Current state: Select all checkbox selects only the 10/25/50/100 on that page

Desired UX: Option to select ALL, free of pagination

(Zapier has a good version of this when you are importing data into a Zap)

Use case: User segments larger than 100, especially those upwards of 1000

Impact example: I thought I had applied a custom role to all the pages in a 250+ user segment. A few days later, a support ticket revealed that I had missed a large number of the users in that segement. Likely because I assumed Select All had included them or because I missed the bulk action on that page of the segment.