You still need a place to live, selling your only house isn't as easy as it seems. Expensive properties usually need months or even years to be sold and you have dozens of people walking around the place you're living in every week. It's an extremely annoying and tiring thing known only to those who tried to sell their house at some point.
For me it would be impossible to use it as an investment because I'd have no place to store my stuff. I'd have to sell all furniture and personal items or hire some containers and keep it all in for months while I'm squatting with my friends or in a rented apartment. I'd rather take a loan and invest it.