CRISPR is not used for any treatments yet because we dont know if any crispr based treatments 1) will work in humans or 2) are safe. there are no FDA approved crispr based treatments. there is virtually no human data on whether crispr treatments are safe in humans.

in cases where a patient has exhausted all treatment options, they can choose to enroll in a clinical study of an unapproved medicine. there are generally dozens if not hundreds of clinical studies for a given cancer type. if a patient is eligible for trials, these days they have plenty of options (however many pts are not eligible for studies). crispr based treatments would be one of many options

the 5 cancer studies of crispr treatments cited in the paper are all chinese studies, and all of them are basically crispr versions of therapies that work. for example, three of them use crispr to remove a gene that makes a protein called pd1. there are approved drugs that treat cancer by blocking PD1, and the safety of these is much better understood than crispr therapies.

for the patients in the crispr studies in china, there are drugs that essentially target the same disease related protein that are known to be fairly safe. so the patients could get a drug that probably works roughly as well as the crispr treatments but with less unknowns about safety

Well, there's that crazy guy who's trying to make it available to the public for at home experimentation. He already tested it on himself, trying to get himself bigger muscles as I recall. One of the comments I saw from a microbiologist included the words "the most cancery cancer that ever cancered".

It's also likely that treatments where you can actually screen for mutations extensively will be more successful. The issue here is you get a lot of mutations that aren't desirable, if you can grow lots of different cultures and ID the ones that are OK, maybe that can work.