Because it brings it into the 21st century, quite frankly. @bluegreygreen has put it much better than me. I think a some of the Scandinavian royals have done this to streamline their monarchies.
I think KC should have done something similar, when he ascended. I’m a constitutional monarchist (got splinters, according to my mum), and I see no issue, with it.
If the monarchy want to survive into the 22nd century (and I have my doubts), then they need to adapt, sharpish.
IMO that means titles for monarch, spouse, heir, spouse, their heir and spouse and any working royals.
Working royals get to keep if they have retired eg like Duke of Kent and not kicked out like AMW. So no titles for Charlotte, Louis, Sussexes, Yorks etc unless they are working royals they can be styled like James and Louise.
edit LOUIS