What happened to the days when men wore suits as casual wear men in the 1950’s men in that era used to dress up in suits as every day apparel?

No one wore suits casually. It was only for work or formal occasions or church. Otherwise they wore regular clothes like we do. Jeans, t-shirts, overalls, work coveralls, etc. My dad wore jeans and button-down shirts. My grandad wore overalls with a t shirt underneath.