Because it’s far easier for someone with a great vision about how to use the state’s wealth for everybody’s benefit to get themselves elected to the governing body than it is for them to get themselves reincarnated as an aristocrat.
It’s still there at an institutional and cultural level - I think the most glaring example of this is the amount of landlords who either openly or discreetly (with a phone call to your realtor) will not rent property to foreigners.
At first the supposed religiousness of it annoyed me too - but over time it sat ok with me. If you think about it, the audio course they use for the sessions was recorded back in the 90s, and back then this was refreshingly religion free. Lots of the work on meditation (things like Search Inside Yourself) which have completely reduced the amount of religion in it, are very recent compared to Goenka's course, so I think you have to take it as a product of its time. With a partial Indian background, a few times I've tried Indian writing on meditation, etc, and it is so seemingly intricately bound up with religion (almost to the point of superstition), that to extricate it as much as Goenka did for the vipassana course I think is still great work.
Unfortunately I have to agree that it does attract a lot of participants who want to believe in magic and superstition. I was very disappointed when the course was over and I found this out. Perhaps that is why Goenka is very clear in the recordings to be skeptical and only take what one finds useful from the practice.