Partially it's probably a price thing, like £2k for sperm, £1k for IUI, multiplied by however many tries it takes (5-10?) (see https://www.marketplace.org/2019/10/24/the-cost-of-building-a-family-using-donor-sperm/), and people who can afford that easily already have lots of ppl in their dating pool as successful as sperm donors so the benefits are less clear.
wonder if making intrauterine insemination more accessible is possible / would have large benefits or whether anything feasible would be meh and not many people would want it anyway