I strongly doubt that those with a £12k package actually do struggle (unless you've spotted anyone posting on TSR or you know someone). Inexperience would e the only explanation for that - or some kind of expensive bad habits!
The ones who have the trouble are those whose household income pushes them into the lower amounts of Maintenance Loans, but then find that their parents either can't or won't help with finances. There have been posts by people in this section over the past few days, from folks whose Maintenance Loan won't even cover the cost of their accommodation, and yet their parents are not going to contribute for a variety of reasons.