Juniper76 spoke with FS today and he mentioned that he used to prescribe pregnyl, but doesn't anymore as there is no evidence that it increases the chance of a successful pregnancy.
It's not something that increases egg quality or anything like that, it's just luteal support. I realise I don't have his expertise or professional experience, but my personal experience has been that it is a very effect method of luteal support. There was a shortage in recent years, so maybe he decided at that time that it wasn't worth the effort since there were more readily available alternatives? Who knows? But after doing an IUI cycle with 250iu FSH (which was enough to have AF arrive early when I was just on 2x crinone daily), I used only 3x 1500iu pregnyl boosters (3, 6 and 10dpo) with NO progesterone and had a 17-day LP, so it clearly worked very effectively as luteal support and 3 injections over the 2ww is a LOT easier than 30-50 crinone or pessaries... A high enough dose of progesterone would achieve the same degree of support, so it's not the end of the world if he doesn't prescribe it any more (as long as he gives you enough progesterone)...