It's cool that you have not encountered any issues but especially birth control pills are also no smarties but many use them as they were candy.
In my personal circle I only new of a single woman who had no issues. The majority had all flowers off issues. During and afterwards. No most of the time it got downplayed or simply ignored but doctors and society a like.
I'm personally glad that birth control pills are not longer sold as a wonder pill because many woman suffered needlessly and the worst part is that many did not knew that is was the pill in the first place.
I already answered why, it's chemistry. Everyone has side effects, not everyone notices them. You can not introduce a medication, or any substance for that matter, into the human body that does not have any side effects — it's impossible.
Normally when people say side effects they mean things that you can actually observe. Hence your earlier point about going off the meds and noticing a difference. If I don't notice any difference other than I don't think your point really stands.
you don't experience side-effects now, but you will if you need to stop taking it