For some people anything “stylish” is not tznius. Well WE made it stylish. WE started layering it because all these short sleeved tops were cute and they could not be worn so OUR girls wore them on top of tznius longer tee shirts. Then the look caught on among others and other girls started layering on the look. It is OUR frum nursing students who wear long tees under their uniforms and scrubs, and our frum female docs who do the same. The style just kept catching on.
And sleeveless dresses are now being worn on top of tee shirts, well guess what WE wore those as kids as well, at that time these sleeveless dresses were called “jumpers”.