Angled walls pretty much defeat the usefulness of most free standing furtniture.
In my lounge my radiator and needing to be able to pass cables through from the electrical sockets also does. Also with there being no garage or shed, I was needing to maximize storage space.
£600 for a double Ikea PAX wardrobe at the time - they were not only half as narrow as my fitted one, but being unsecured units as well as how thin they were meant they would collapse forwards a lot - people warned my about this on Ikea related forums when I was considering then.
Also wanting a corner L shape unit to fit the space that I had, the ikea corner units had diagonal backing as well that would block a lot of usable space. The 2x2 in L shape fitted plan I got had no backs, which means I can fill them up all the way to the wall, top to bottom and front to back.
Also the cost of fitted furniture minus any cost for age / degradation can be added to the valuation of your property if you decide to sell in the future, and you can try to base this on the non discounted price.
A lot of houses with no garage or space for even a shed need to try to maximize internal storage.