... is to dupe the unsuspecting customer. The "sucker", that is naive not to know enough about what they're buying and on impulse just buys it, thinking they got themselves a super deal. These fakes are not engineered to fool the collector or smart person who uses an authentic watch photo to compare.
Making watches has large overhead costs behind it, if you're building quality. But if you're building junk, it's a very different story. I suspect that as watch making equipment gets replaced with more modern and high tech machinery, the much older less capable machinery gets sold off at bargain prices. Also... a fake watch maker is definitely leveraging the outsourcing of parts from various 3rd parties. The stamping out of plastic in the shape of bezels, dial faces, and bands, is likely done by a 3rd party that may not even have a clue that they're creating a part for a fake watch. The name "Casio" may be applied later at the fake watch maker's factory. The most difficult part to duplicate effectively is the case back. The metal type and the imprinting on the back of it requires good quality metals and precise machinery. This is why the easiest way to tell a fake is to see the back, which is why fake watch sellers often omit backside photos or provide them slightly out of focus.
I'm pretty sure that we won't ever see a G-Shock watch copy that requires a magnifying lens to tell the difference from a real one, because the extra effort involved to reach that level of simulation is just not worth it to the maker. They want to do "just enough" to dupe the unsuspecting buyer. The G-Shock watch collector or aficionado will not be fooled. It's true that fakes have gotten better, so much so that at first glance the G-Shock collector wouldn't catch it. But after taking a good look at it, the expert will notice it.
Where the serious problem would be is if a fake G-Shock watch maker would manage to outsource top quality parts and make a very convincing copy, then find a way to leak these into an authentic supply chain. I think this may have happened before, but was discovered in due time.
The biggest problem is with retailers. Some enterprising @ssholes have bought authentic G-Shocks and then returned them swapped with fakes that they'd managed to buy. The sales clerk at the store doesn't have a clue and accepts it, repackages it, and then sells it to the next customer. Because the customer usually tries on the store display, then walks away with a boxed item that they didn't open in the store. So, ALWAYS make sure you check out the watch you're buying first-hand in the store. It doesn't take long to do and just saves you the aggravation.