If there any reason why there are no 802.11AX network adapters (except for Intel AX200)?
There are tons of routers available with 802.11AX already but nearly no client devices. From what I remember at the time of release 802.11AC, there were a bunch of adapters released along with the routers.
I specifically don't like the Intel devices because you can't use them as Access Point mode in 5G bands.
Yeah the AX200 is so cheap and was first to market, so it's the de facto standard desktop chipset. Intel also bundles it with most of their chipsets these days so it makes almost no sense for any PC vendors to spend additional money on something included in the motherboard.
Broadcom and Qualcomm all have 802.11ax client chipsets for smartphones and those are arguably higher market share already compared to the Intel AX series.