Kate Gregory has outlined the answer, but perhaps more detail is necessary for non-native speakers to understand the underlying assumptions.
First, in the Time article the writer is using an extended metaphor sometimes referred to as a "literary conceit":
In literature, a conceit is an extended metaphor with a complex logic that governs a poetic passage or entire poem. By juxtaposing, usurping and manipulating images and ideas in surprising ways, a conceit invites the reader into a more sophisticated understanding of an object of comparison.
The "more sophisticated understanding" we are being invited into is one involving standard, commonplace tropes from romantic breakups.
First, the title refers to the standard plain-truth version for ending a relationship that is usually given by a third-party to the person being jettisoned:
"He [or she] is just not that into you."
In other words, it's over. Get past your issues with the breakup and move on with the rest of your life. In the context of banking, banks are being told by the third party (Time) that consumers really don't care about them anymore.
Here's where Kate's answer enters the picture. The standard trope "It's not you, it's me" — used to absolve the other party in the relationship of blame as a way of pre-empting any desperate attempts to salvage it: "But I can change!", "We can work it out!", and so on. By taking responsibility for the breakup there is no possible comeback. The person on the receiving end of the breakup is left without recourse.
Now, we have to address the fact that this trope is inverted: "It's not me, it's you." That plays the trope for laughs, since instead of absolving the jettisoned party of responsibility, the person broken up with is saddled with all of it. In this case, the banks are being seen by consumers as bearing all the guilt for the relationship falling apart, and are (by refusing to use banking services) being told so by them.
By using such devices, the writer presents the information in a light, clever style that is not strictly suited to the bald representation of boring facts about banking, but which is no doubt much more readable for the same reasons.
There are many metaphoric phrases to indicate randomness, several of which relate to gaming
toss of a coin
flip of a coin
throw of a dart
spin of the wheel
luck of the draw
cut of the cards
your guess is as good as mine
Some expressing lack of control suggest futility
chaff in (on) the wind
a drop in the ocean
like looking for a needle in a haystack
snowball's chance in hell
a face in the crowd
Phrases suggesting a causation, rather than lack thereof, tend toward other images often based on scientific or mechanistic processes or human industry
laser-like precision
as sure as night follows day
in lock-step
you reap what you sow
you get what you pay for
what goes around comes around
you can bank on it
like clockwork
"If you build it, he will come" (reference to the movie Field of Dreams based on the novel Shoeless Joe)
A few dependability references do use gambling metaphors
bet your bottom dollar
a sure thing
ace in the hole (implying you have a hidden advantage)
a safe bet
Some are based on questions, occasionally scatalogical
Is the Pope Catholic?
Does a bear shit in the woods?
Does a tiger have stripes?
Will the sun rise tomorrow?
Best Answer
A Google Books search finds only two instances of "it's not even funny" in its literal (or arguably literal) sense that antedate the first appearance of the idiomatic form of the phrase.
A headline in the Columbia Alumni News (October 20, 1922) proclaims "This Is No Joke!" with the subhead "It's Not Even Funny." And an advertisement in The Journeyman Barber, volumes 24–25 (1928–1929) [combined snippets] has this bit of doggerel:
The next two matches, however, use the form of the expression that the OP asks about. From The Parchment (volumes 5–8) (1933–1937 [exact year uncertain]):
And from a metrically atrocious poem called "Safety First" that appears in Trans-communicator, volume 53 (1936):
An Elephind newspaper database search finds this instance from "An Australian Girl Abroad: Radios Are Cheap in London: Midget Sets From Three Guineas Up" in the Narromine [New South Wales] News and Trangie Advocate (March 7, 1939):
The implication of the expression, even in the 1930s, is the one that AHuman notes in a separate answer: Our first inclination when presented with a minor inconvenience may be to make light of it and perhaps to laugh at the absurdity of the situation or at the incompetence of those responsible. But as the level of unpleasantness increases, its seriousness becomes less and less escapable through laughter, and we finally reach the point where "it's so bad that it's not even funny."