My husband and I have lived below our means for most of our marriage. Because of that, we are now in our mid-50s and don't work at all. Other than taking a decent vacation every year, we still don't do anything extravagant.
Because he was smart.
If you want to stay out of debt, you "live below your means" ... You save money from your income ... You don't spend more money than you make.
Orwell was a complex character, by turns communist, and liberal.
He suffered from chronic ill-health for most of his adult life and for a while must have wondered whether he would ever be able to support himself.
His family came from the wealthy middle classes, but little of that money trickled down to him.
Early life for his family was difficult as they tried to maintain an air of middle-class gentility without any money with which to do it.
All of these, together with a minor battle with the tax man meant that in later life he was constantly aware of how close the breadline was.
He also, for a period of his life, deliberately chose to live simply, in a remote corner of the British Isles - because he preferred it, not for any other reason.
Did any of that help?
Sources: Wiki, BBC History and the dust jacket of a copy of "1984".
I currently live below my means, why? Because then I have money for the future in addition to my retirement.
Living below your means builds in a "Comfort Zone". It allows for you to not only save for retirement but have available cash should a financial burden arise . . . Illness, Laid off or fired from job, fire or car accident not covered 100% by insurance . . . Legal issues . . .
Living AT your means is only one "Life Issue" away from debt.
Living BEYOND your means is immediately an issue with debt.
The type of work Orwell did is one that "Ebbs and Flows", you could live quite well off of the money from writing a good book, but the in between times until the next good book would be financially lean. Its best to find that average income based off of the highs and lows, and fix your budget just below in this type of career. This will also go a long way to alleviate stress to make life more enjoyable. Perhaps Orwell lamented in the differences of the different social classes and had more socialistic ideas of government in mind (Animal Farm seemed to tell this).
"Living below your means' simply means you don't 'live above your means' .. "Living above your means" - means you live a lifestyle that you can not afford. Borrowing money and getting into debt that you seem unable to pay off in a reasonable amount of time. It really is not very 'smart'.
To to answer your question .. I imagine he lived 'below' his means because he wanted to be smart about how he 'lived'.