Honestly?
I have a few reasons gathered over the years. It's nothing personal and not aimed at anyone in particular but my observations from working in the club/lab and edge and vibe.
Im speaking as a former CM; apparently every 10 year old is mature...they're often hard work and don't have the social skills for edge, they often don't have a filter and can be inappropriate without meaning to be and it's just draining. As an edge CM your just sorting out petty issues between kids, much more so than the club and lab. Is it all kids? No of course not, some were amazing and you'd think they were way older. And Of course there's 11,12,13 year olds who act a lot younger. I just wish there was something like a one strike rule, you mess up your back down to deck 5, but that would never happen at Disney...
And to be honest, it was the entitlement (90% of the time) that would come across when some parents would ask/demand 'so, my kid is 10 but they're really mature and hang out with 13 year olds every day of they're life and the lab is really babyish, even thought they've not set foot in it, and I paid a lot for this cruise so.....' when that happens multiple times every few days, it's just makes you bored of hearing it.
Is used to really upset me that older edge kids felt they had to age up to vibe when sometimes they didn't really want to but needed a break from kids (at 10, the majority, not all, are still kids, not tweens).
And then there was the older vibe kids that are now over run with younger kids, are you going to allow them to age up into adult areas? Of course not, we've all seen the angry posts if someone even suggests that their 17.5 year old can sit quietly by the adult pool a read a book...
What's the point in having age groups of your not going to stick to it. Just make edge from 10 years and solve the issue....of course then all the 9 year olds would want to come.
Don't get me wrong, I don't have anything again 10 year olds, I know it's sounding that way. My issue is with Disney lol.
I truely feel disney need to sort their age groups out, it's one of the reasons I left, but in my opinion 10 year olds in the teen areas isn't the answer.
However, PC and TA cruises would be the ones that I wouldn't mind bump ups, the whole ship has a completely different atmosphere, and the clubs are quieter and nicer having some kids around than none, but if you get ones that are hard work, you have time to mould/break them lol. Just don't expect them to be constantly entertained on the longer cruises in edge like they might be in the club/lab, there's a lot of down time on longer cruises, but the kid/Counselor relationship is completely different in a much nicer way.
Ok, flame away