Why is it that nowadays people like wearing flip flops everywhere?

Why is it that people like wearing flip flops a lot? What made everything change from like 20 years ago. I really don't remember people back in the day, like in the 90s wearing flip flops 24/7. The only places where you saw people wearing flip flops while I was a kid, was at the beach or by the swimming pool but that was about it. My mom even told me that the same time applied to 80s and 70s. People wear not accustomed to wear flip flops everywhere they go, specially in a Public place or work place. It might be that they back in the day flip flops were look down as a sign of laziness, cheap, and unprofessional. From what I can noticed, flip flops didn't start to became as popular as they are now until the mid 2000s came. That's went the trend of wearing them started to grow so much. Flip flops are so popular nowadays that most work places are starting to allowed their employees to wear open toed shoes like flip flops, which looks super unprofessional in opinion. If you don't believe me here's a photo of what it looks to be a team photo from an AT&T Call Center here in the states. As you can see theirs in the photo at least three female employees wearing flip flops at the call center. Also, not that long ago I went to the Apple store to kill some time while my girl was shopping for sone new clothes, and while I was their checking their new products, next to me it was standing what it looks to be the store manager speaking to a couple of customers wearing a pair flip flops.