What is the difference between using an ND filter versus 2 polarizers?
One thing I was always wondering when it comes to ND filters is why there's need for such a large amount of different strengths, when two linear polarization filters would do the trick just fine. Assuming a light loss of 1/sqrt(2) per filter, one could easily create a ND "1 to infinity" filter. Why is that not in everyone's camera bag?
Unfortunately, all the filter companies offer only LCPL (linear, then circular), so I can't simply make one myself. Apart from cases where I do not want to take polarized light into account while having a ND filter (architecture photography maybe), I can't think of a reason not to do this.
Edit: More specifically, I'd like to know why there's nothing like this at all, or how I could get my hands on such a filter.