[D] On conferences and page limitations

What is your opinion on long appendices in conference papers?

I am observing that appendix lengths in conference papers (ICML, NeurIPS, etc.) are getting longer and longer, and in some fields they are now basically the standard and a central part of the paper. From my point of view, this is becoming a bit problematic. I have many times been asked to add more experiments which, in order to be included, require several extra pages beyond the main 8–10 pages. This effectively makes the appendix a mandatory part of the paper.

Isn't the whole concept of page limits in conference papers that the main pages should stand on their own, and the appendix should only contain secondary material that is not really necessary for understanding the core contribution?

If the standard becomes, for example, testing on 100 datasets or including massive experimental sections that cannot possibly fit into the main paper, then the appendix stops being supplementary and becomes essential.

I believe that the natural place for a 25 pages long paper is a journal, not a conference with a 9-page limit.

I am curious how others see this. Is this just the new normal now?