This question is about jobs in general, but can be seen as being more specifically about "technical" jobs such as programmers and web designers. In the field of technology, people regularly take time off of their jobs in order to write books, organize seminars, attend trainings, work on open source projects / their own personal projects, and for other personal reasons such as travelling, visiting family and such. In all of these cases, during a certain period of time (maybe a month, six months, or a year), the person is doing fine without having a "normal" job.
Despite this, we seem to always recommend finding a new job before quitting the old one. I don't understand why this is necessary. I see this idea in the Workplace SE often, but never a convincing explanation of it. It seems that everyone just takes it for granted and assumes, "oh this must be true!"
I have my own life experiences that prove it's not true. I took one month off between two jobs in 2014, and did this again in 2018. I don't see anything wrong with this approach. I was never under any pressure to find a job, because I was well-rested (I was unemployed, didn't have to get up early), had much more time to prepare the interviews, and therefore performed better in the interviews.
What are the valid reasons behind the idea "finding a new job before quitting"?
Response to some of the comments:
Q: How did you pay your bills when you were unemployed? How long could you have managed that for? – Philip Kendall
A: I assume we all have bank accounts which are not completely empty. The advice might make sense for those who are struggling to pay their bills, but the assumption "everyone relies on the monthly salary to pay bills" isn't true.