For instance, I remember the time when chatting online (even with people you knew offline) was considered to be a nerdy activity. Then it gradually became more mainstream and now it's the norm to do it and a lot of people do it multiple times per day. This fundamentally changes how people interact with each other.
Another example is dating. Not that I have personal experience with modern online dating (enabled by smartphones) but what I read is disturbing and captivating at the same time e.g. apparent normalization of "ghosting"...