I have not seen any visible moire in any of my images since shooting a 6 MP Fuji S3 Pro more than 13 years ago. It was really poor at rendering high contrast lines which appeared at an angle in images...like power lines against the sky. Still have some images demonstrating that. Early Samsung HDTVs were similarly poor rendering angled lines...many times the shafts of golf clubs would completely disappear as the player was setting up for a shot. In that case, though, their early DSPs (Digital Signal Processors) were not up to par, but the results were much the same. This effect could also sometimes be seen when attempting to copy halftone images on a copy machine. That's why many of them had special settings for copying anything other then text.

I do not know the answer to the question of why some sensors don't have AA filters, but in looking at the table of pixel pitches above, I suspect that the answer may be that it has nothing at all to do with need or desirability. Rather, I suspect that it may be simply too difficult to fabricate reliable AA filters with proper geometry at the smaller pixel sizes, at least right now. Many years ago, when I was working in the semiconductor manufacturing industry, the design and product engineers had an inside joke around integrated circuit design. It was simply, "If you can't fix it, feature it." I later heard stories about the same attitude being prevalent in the design of early PCs.