You're assuming that 'the market' is some kind of objective mechanism which filters out bias in the name of profit. The business case for 'diversity' has been presented for decades. In the context of this thread, bike manufacturers can't be bothered to fill female-shaped gaps in the market, and for various reasons including those mentioned by
friendofdorothy and
Yuwipi Woman there is little evidence of actual demand in that so-called gap.
It looks like the bicycle business is designed for men, not surprising that men are baffled by market gaps and fall back on some kind of 'money is gender blind' premise.
There are many gaps in many markets; they exist for lots of reasons. At firm level, the gap exists because there is no compelling business case.