Yeah I don't understand the default assumption of "people are mostly lazy when working from home" that many managers seem to share.
I find I work harder from home, given there are less distractions from nattering colleagues.
Also, surely they need to have better methods of actually monitoring employees, then there'd be no need to assume anything. We've worked effectively from home and thankfully my manager agrees, but friends who work for other employers say they really feel they have to go above and beyond to prove they're not slacking at home.
I've felt the opposite re the proving myself while WFH.
When I was in the office I felt watched, I felt under pressure every second of my day as I was so busy. If I wasn't at my desk my manager would give me a look, as if to say 'you're too busy to be in the kitchen making a cup of tea'. If I spoke to any of my friends at work i would get told off! (Like I was 15 in the classroom again) So it resulted in me hardly getting up from my desk for 8+ hours a day out of fear that my managers were thinking I wasn't doing a good enough job. This turned into some major anxiety issues, panic attacks and having to take time off work.
Since being at home I actually get more done, because I'm not panicking. I'm not rushing and worrying and getting myself into a state about how much I had to do and if I was being watched or not. Now I am calm and I know what I need to do and I feel free to take a breather if I need it. This has made a huge difference to my productivity. Which my manager has actually recognised, apologised for and agreed that working from home works best for me.
I know some people have used working from home as a way to take the piss and so the bare minimum though!