of course you can waste time in the office as well, from people joining every meeting and asking "but does it scale" to people playing table tennis, but in general its harder to do than remote
Roll in at 9:30 and complain about traffic. Spend until 10 easy getting settled in for the day: making coffee, slowly sifting email, recollecting the weekend with others, bathroom break, etc. Now its the first meeting, totally irrelevant to anything you do so you zone out. Suddenly its lunch time. Another hour goes by. It's 1pm now. Check email. Another meeting. Check instagram. 3:30pm. Let me fire off that one email. Wow look, 4:35pm, better leave now to beat traffic.
I've seen people make respectable careers out of this.
It’s much easier to schmooze in the office than at home but it’s possible at home if you have good relationships with your colleagues, so when you’re not in meetings, slacking or doing slack huddles to talk about your weekend are good for morale and so good for productivity.
Granted this can completely be abused but I think it’s an important distinction.