Per User:Nick_Moyes and @TheDJ at https://www.mediawiki.org/wiki/Topic:V6nknm0p8uc8mtao people who read Wikipedia articles on their mobile devices are unable to sort tables, even when the tables are marked as sortable in the wikitext.
|Open||None||T111565 [EPIC] Enable mediawiki.page.ready on Minerva (collapsible templates (including infoboxes) and sortable tables)|
|Open||None||T233340 Add sortability to sortable tables for readers of the mobile web site|
The mw-collapsible code and the sortable code are currently tightly coupled - so enabling sortable requires enabling the other as well. We could modify core to make it possible to do one without the other.