The following explanation has been provided for the high rate of females who cannot achieve orgasm (and instead fake it):

Pavlicev and Wagner (2016) contended, it may be a due to the fact that there are not enough high-quality men to go around. In other words, some of the variance in orgasm frequency among women may be a consequence of variation in access to high fitness males, and this may apply especially to women suffering from female orgasmic disorder.

[...]

Consistent with our hypothesis, a study of sexual dysfunction found that the incidence of orgasmic disorder in women was inversely proportional to their level of education, and unemployment was also a risk factor (Safarinejad, 2006).

I.e. women who cannot get access to high status men will not orgasm as much (odds ratio of orgasmic disorder with low education status is 3.13, 2.21–4.41, 95% CI).

Further support for our idea that female orgasmic disorder may be an artifact of an inability to access high-quality male partners comes from a recent study by Kontula and Miettinen (2016). [...] Even though attitudes and sexual practices have become increasingly liberated in Scandinavia (and elsewhere) over the last 3 decades, they failed to find an increase in female orgasm frequency among Finnish women during this period in spite of their greater openness about sex, an increase in number of sex partners, and more frequent masturbation.

In stark contrast to widely held views among clinicians and others that in orgasmic females suffer from sexual inhibition and related psychological problems, this study stands as strong testimony to the contrary. The authors concluded that “the improvements in gender equality and sexual education since the 1970s have not helped women to become more orgasmic.”

Quite frankly, I'm currently not seeing how the latter serves as further support, but still an interesting result.

https://www.researchgate.net/profile/Gordon_Gallup2/publication/319414654_An_Evolutionary_Perspective_on_Orgasm/links/5ace63a14585154f3f4522bb/An-Evolutionary-Perspective-on-Orgasm.pdf

I'm surprised that this recent literature review does not discuss the possibility that female orgasm evolved because it signals arousal and female arousal is necessary for (consensual) intercourse to occur at all. Hence men are selected to regard female orgasms as a highly valuable goal. This in turn selects for women who display greater orgasmic capacity etc.

Of course my favorite explanation is still that female copulatory vocalizations are mating calls.