I think in this day & age and financial climate it's pretty acceptable as long as the DC aren't taking the piss. Most of my friends left at some point in their 20s, usually early to mid 20s- a combination of financial viability and geography usually kicked in. When I was at home, I did have quite a bit done for me, but it was more due to me working long hrs & getting home late. My mum a) felt for me b) is quite dominant and bc is at home all day so did whatever needed doing in the day. She didn't want me coming in and clanking about with stuff when she was settled. I did pitch in as much as I could though.
I boomeranged between 16-25/,6. Boarding school, uni, year out with voluntary work, post grad... coming and going with a plan to be out properly and moving in with then BF by 23. Instead I had a set back in life at 23, a few months of paralysing shock and nothingness and starting from the bottom with a very badly paid job. I couldn't afford to leave home on my wages round here & I was in no state to be away from family! Went into rental a month after my 26th, when I finally earned enough. Bought my 1st place in Jan this year & I'm 30 this week. Did a month at home in Dec due to contracts for rental & purchase not lining up & no wish to do it again, as much as I love my family. We love each other and I have a lot of space & laissez faire but I missed my autonomy. Now my home is my own and I no longer share, I feel much more able to host, too.
Of the people I know still at home, my bf is 29 and similarly has boomeranged thanks to uni, time out, moving for work & a costly set back but is saving to leave properly now. I don't judge that. It's hard. A friend has a mid 30s brother who has struggled with decently paid work (free-lance sound engineer). Family are wealthy & he "is responsible" for their large London home whilst his parents live abroad 90% of the time. They are fortunate in their set up. Another family friend is at home in his 40s with an inherited a stake in his parents house from his GPs. I think he feels both blessed & cursed. They're happy and I don't judge the set up, they're lovely but I think he'd be happier in a relationship, living with a partner... but what to do about the family house.
The only person I judge for still being at home is my immediate ex. He is 30 and claims it makes financial sense to be at home despite a £££ Hampshire-London commute on top of insane hrs. He gets nearly everything done for him at home so rarely lifts a finger, and although he does pay housekeeping, the current arrangement frees up the bulk of his cash to fritter on luxury goods for himself and feed his self image. There's always a reason why he hasn't found a house share or moved in with mates. Mostly so he can continue buying big ticket items to look the big man. He earns reasonable money/could get by out on his own.