The weekend warrior explained

The expression “weekend warrior” is a common term used on social media and fora when detailing is discussed. It’s not very clear who come up with the expression, but it’s been around for a while. It’s a informal way of describing a person who only irregularly details as a hobby. Most of the time this is done in weekends because most people have 2 days off.

Common use

The term “weekend warrior” is often used when people want to explain that they don’t detail for money, or don’t detail regularly. It can also be used to describe a person who doesn’t detail cars that don’t belong to him-/herself. It is mostly used to describe oneself. An example could be:

Pretty happy with how my car looks after a wash and wax, even though I’m just a weekend warrior.

or

Had my first try with machine polishing. Not a pro though. Just a weekend warrior.

or

As a weekend warrior I don’t wanna spent to much, but what type of XXX is good value for money?

Why a weekend warrior?

It is not really clear who come up with this expression, but it has been around for a while. Google search results show that there are results as old as from 2004. Before that time it was already in use to describe anybody who did jobs around the house in the weekend. A person who builds a shed in the weekend could refer to himself as a weekend warrior.
Besides, “weekend warrior” would probably sound a bit better then “car detailing type of home improvement guy”.

The humor behind it

The use of the word has a little irony. People on the internet often refer to themselves as “just a ….” or “only a …” as if it is something that is nothing special. Taking away the respect and pride that should come with the label.
And the other side, the term “warrior” is not just a simple term that is given away to anybody. It used to be a title and/or reputation that one should earn. Working hard to be allowed to call him-/herself a warrior. Not some trivial, small thing.
So on one side people formulate their sentence in such a way that it takes away the respect it deserves, on the other side it includes a word that requires hard work and should be respected if earned.
But it is not very likely that this irony has been done on purpose.