I think there are simpler explanations:

1) historically, wealth has often been obtained by violence, corruption and other less than ethical means;

2) even if it was obtained legitimately, most societies expect the wealthy to donate a significant portion of their wealth, slowly making them less wealthy;

3) (and this is probably the strongest one) the appearance of wealth or poverty is what matters, it's very frowned upon to flaunt your wealth while humble living is seen as righteous.

4) (this one is controversial) it's a coping mechanism, especially in cases of severe generational poverty where people have given up trying to climb the economic place (and quite possibly for good reason).

This is particularly true in Christian societies due to that passage you quoted (and others like it in the new testament) but it does appear in all societies.

I'd say the evolutionary argument is relatively weak to all of the above.

Bold of you to assume the Bible is written to benefit its target audience. The message is "don't seek riches, don't question, stay down, stay humble, be placid and obedient, all truth comes through me." Who gains from this philosophy?

As for 'proud to be poor' it's an interesting expression indeed, I read it more as 'proud of what I've achieved with the limited resources available' rather than 'proud to only have limited resources available.'

Looks like the bottle is pushed up from the bottom (so the water won't pool around the joint) and then caulked with some kind of sealant. Since these are basically shanties with corrugated steel roofs I would think that leaks would be the least of your concerns. And since plastic bottles come from the waste stream anyway I doubt that replacement after a few years would be an issue. Depends on what happens after a few years of UV exposure... if the main problem is just the plastic becoming hazy, well, that just gives you a free light diffuser!

I think the general idea is that you can reuse any sort of plastic refuse (PVC pipe is also common and it's UV stable), add water to improve the optics, and tada, even, diffuse light without an actual hole in the roof.

Litro de Luz/Liter of Light is the current org carrying this idea forward AFAICT.

The question of leaks is directly addressed, although roof material isn't mentioned:

"You fix the bottle in with polyester resin. Even when it rains, the roof never leaks - not one drop."

Questions of durability are absent, but with the number being deployed, answers should be available shortly:

"In the Philippines, where a quarter of the population lives below the poverty line, and electricity is unusually expensive, the idea has really taken off, with Moser lamps now fitted in 140,000 homes."

It seems the cap is the most UV-sensitive part, and that is solved by adding something to protect it: "The lamps work best with a black cap - a film case can also be used".

There are already solutions for mounting a small led lamp with a battery and solar cell in place of the bottle cap to provide light into at least the early evening hours.