There are too many dances now for the couples to do all of them. Last Series was 9 weeks long but there are now 15 dances in the schedule, meaning each couple got to drop loads of dances (dances repeated in the Final so that doesn’t count) so it’s “easy” to drop a perceived harder dance. This Series will be, I think, 13 weeks inc the Final so there are 2 competitive weeks left before they repeat dances in the Final.
From my back of the napkin calculations (via Wikipedia), the current remaining couples have the following dances to choose from:
AJ & Kai - Quickstep, Tango, Rumba, Salsa and Cha Cha Cha
John & Johannes - Waltz, Foxtrot, Jive, Salsa and Couples Choice
Rose & Giovanni - Waltz, American Smooth, Rumba, Salsa and Charleston
Rhys & Nancy - Foxtrot, Tango, Argentine Tango, Rumba and Samba
Dan & Nadiya - Waltz, Tango, Argentine Tango, Samba and Salsa
On the basis that they usually, though not always, alternate ballroom/latin type dances Dan is up against it with a choice between Samba and Salsa, and Rhys could be undone by a Rumba.