A simple answer is: working from home requires the ability to hold yourself accountable for your productivity to a much greater extent than if you were in an office. Yes, working at home is a different setting, with different distractions, but, based on my experience, there are a lot of extra motivators present in an office, like peer pressure, justifying the commute, being held accountable for the perception of working, contribution recognition, easy socializing, etc.
For better or worse, none of those are as impactful when working from home and the worker is forced to fuel their productivity themself.
I left my job a year ago to work on my own projects full-time and it took several months for me to find ways to really motivate myself to be consistently productive