In the computer industry, everyone (more or less) dressed in suits--though not necessarily white shirts--at industry trade shows. Then, one year at one of the b

In the computer industry, everyone (more or less) dressed in suits--though not necessarily white shirts--at industry trade shows. Then, one year at one of the big conferences, the IBM squad showed up in polo shirts and most companies more or less collectively decided that if IBM wasn't wearing suits any longer, they didn't have to either. This was around the time of "casual Fridays" and a general growth of casual business attire in companies more broadly.