I suspect tight/see through clothing can be a combination of many factors including:
. Deliberate decision to wear tight or transparent clothing
. Poorly manufactured (cheap) clothing that is “threadbare” even when new
. One gains weight and is not at the point where they wish to purchase new clothing, or perhaps can not
. Awareness or lack of it (it is possible someone who gained weight or clothes shrunk in dryer is not aware of what they look like from behind)
In general, it is never a good idea to discuss the way your neighbors husband, wife, son or daughter dresses. That is best left to their husband, wife,father or mother. You can speak with their Rav or Rebbetzin to discuss it with them if you believe it needs to be discussed.