Why do some of my peers "forget" to say "thank u" after being helped?

Why do some of my peers "forget" to say "thank u" after being helped?

2018-11-06    15'14''

主播: Harrison Yan

380 3

介绍:
随着我离18岁越来越近,我发现越来越多的同龄人不懂得感恩了。这是为什么呢?