What does “it’s not going to suck itself ” mean?

Question

In Goa, I see tourists wearing t-shirts that have the following text on them, along with a red arrow:

It’s not going to suck itself

What does this mean?

Answer 1

It refers to the genitalia of the (presumably male) person wearing the shirt.

(I hate offensive tourists.)

Answer 2

These t-shirts are apparently not limited to Goa, but appear to be rather distressingly popular, coming not merely in t-shirts alone:

but also in many other formats, only a few of which are routinely hidden from the public eye:

All these products are saying the same thing: the “it” refers here to a man’s private tackle, so this a man on the lookout for a new fellationship ^{(Urban Dictionary link)} — that is, he’s looking for a blow job from someone else. The phrase “doesn’t suck itself ” further rules out autofellatio ^{(Wikipedia link)}. It’s extremely coarse advertising in search of a fellator or fellatrix to sexually service the fellow.

A slightly less gender-biased variant is occasionally seen, one that might be worn by either men or women because it substitutes lick for suck:

Even if the allegorical ice cream cone on the lady’s t-shirt might bring a smile to some viewers, all these products are extremely coarse, and probably offensive to many viewers.

Answer 3

Matthew has half the answer. The other half is that "{Noun} isn't going to {verb} itself" is a common phrase implying that a task isn't going to get done unless someone (by implication, the person being spoken to) quits messing around and starts doing it. For example: "These dirty dishes aren't going to clean themselves."

So basically this shirt is supposed to be a "clever" way of suggesting that you should drop whatever you are doing and give the T-shirt wearer oral sex. I'm probably no expert, but I'm guessing he doesn't get many takers...