It's not only about wealth but also lifestyle/belief. Some countries deliberately choose those toilets over the ones we are accustomed to.
From an anatomical point of view, what you call "modern/civilized" toilets are actually bad for you, because human beings are not meant to sit in order to relieve themselves, but squat. And medical surveys tend to demonstrate that the sitting position causes some medical conditions (some of them quite consequential) that we wouldn't otherwise suffer from.
Nowadays you can buy little chairs/stools that go in front of your toilet and that you're supposed to put your feet on when sitting, so as to reproduce the squatting position.
So basically it's another case of civilisation thinking it knows best, when the superior practice is that of our ancestors. I get that some people will cling to being "civilized" even if it actually goes against their health. But don't take my word for it, I'm no expert, I just read a few articles about it last year.
The majority of the asian continent uses squat toilets, and with good reason. Sitting is an unnatural defecation position because it causes the puborectalis muscle to be in an abnormal position, which causes not only immediate effects such as greater difficulty going, but also long-term complications such as haemorrhoids. It's not a case of other places being unfortunate enough to not have 'modern amenities' but rather due to our method being wrong and them choosing not to use it.
Yet they are somewhat disastrous from a hygiene point of view, a roadhouse toilet halfway between Nanning and Shenzhen was about as close to entering the Seventh Circle of Hell as I care to venture....there are now designs that offer the best of both worlds.