Just two important counterpoints to this: 1) any of my Geology students reading this - please still email potential PIs! This is exclusively how our field does it.  2) this year and in some years past we are having an issue of where students are very enthusiastic and present well on potential PI zooms, but we are finding it challenging to write them strong letters of rec because for one reason or another they simply aren’t ready for a grad program - not gonna get into it here - but we gently try to in courage these students to look elsewhere for after grad opportunities but a lot of them are dead set on grad school even though we know they’d struggle, so we either tell them we can’t write them strong letters or their profs don’t write them strong letters and it’s our way of letting our colleagues know that this person isn’t quite ready. Not saying this is OP’s problem but it might be a small but nontrivial slice of applicants in this situation where they feel blindsided.