The marketing department at ROH is relatively underfunded. Like a lot of organisations their focus ( for good or bad) will largely be on attracting new ( and younger audiences), plus taking into account requirements from various funding streams.
Appreciate lots of people ( possibly correctly!) think the marketing they do isn’t great, but it isn’t done without thought ( for example using rehearsal photos will have been done to appeal to a certain demographic).
This doesn’t of course mean they can’t be criticised for the approach they take - but it is a deliberate approach.