Otzdarva (big DbD streamer) did a test where he'd always camp survivors on first hook for 1 stream. He was intending to prove why the strategy barely works, but the opposite is true.

If a killer camps the hook, the best thing for survivors to do is to utilize this time in the most efficient way. This means the survivor on hook staying as much as possible, and the other survivors focusing on gens. As Otz is a red rank, and this is the best counter to facecampers, you'd think he'd have depipped a lot.

Instead, he'd constantly get 2-3ks because people want to go for the save. There's also people who will intentionally try to 4%, knowing they'll fail, so they can be sacrificed quicker to get out of a match with a camper, which also isn't helpful for survivors. Again, this was in red ranks, and Otz kept safety pipping. Then you apply this to the other ranks, where there's less good survivors, and you can start to guess why facecamping is seen as a viable strat.

If you camp, you'll lose emblem progress in chaser, which is probably one of two emblems you'll be getting a lot of progress in (excluding the loss from camping) by doing this, so it's definitely harder for killers to pip. You'll eventually pip enough where you'll get out of the ranks where it's most common, until MMR comes back. BHVR sees a 2k as a win for both sides, and guess what can easily get a guaranteed 2k? Facecamping.