The transition to adulthood is rarely easy for any young person, and some find it to be more difficult than others. The reality is that there is so much to think about when it comes to being a responsible, independent human being that many prefer to take the easy option and opt out of putting in the work it takes to get to that particular point.
Naturally, problems arise when someone decides that they are not cut out for adult life. Sooner or later, it is going to become apparent that the path they are going down is not sustainable in the long term. The people who pay the price aren't always the individual who is stuck in a perpetual adolescence, either. More often than not, those closest to them are the ones who have to suffer because they are in denial.
The truth is that everybody has to grow up someday, and there are going to be parts of that process that will be difficult. It is understandable that their loved ones might want to make that journey a little smoother now and then, but that doesn't mean that they should constantly cover for them.