When are there going to be true workstation motherboards? Some reasons for this are:
1. ECC RDIMM - While the AMD HEDT line supports 4 ECC UDIMMS and 60 lanes of PCIe 4.0, the common current Intel workstation deal is to be using ECC RDIMMS and so you would have to buy new RAM to go over to AMD. This is a problem because for me for example I have sunk over $700 into RAM for my workstation and wouldn't want to abandon that to go to AMD. If I were to go to more cores, well ECC RDIMMs are slow and so it would be nice to have all 8 RAM channels.
2. PCIe - It is not uncommon for workstation systems to have multiple PCIe cards in the system. For me for example I have a GPU, RAID card, SAS expander (which could be mounted elsewhere), extra sound card (kept having noise problems with USB cards and have a mix of digital and analogue going on), USB 3.1 Gen 2 card (my aging motherboard does not support this speed), and server NIC (onboard NIC burned out under sustained heavy load). It is not uncommon for workstations to have more than one GPU and other cards such as RAID controllers and network cards. There are no Threadripper boards with as many PCIe slots as I am using.
3. Stability - When doing workstation type stuff, there is no real interest in overclocking, just stability. Threadripper is designed for overclocking instead of focused on stability. I have noticed some motherboard makers automatically overclock CPUs when not specifically workstation / server oriented and this has had disastrous results for workloads requiring absolute stability.
4. Ambient temperature - When I built my current workstation I designed it for ambient room temperatures up to 45 C as it is an always on system and it could get hot in the room I had it in. I accomplished this with the help of custom loop liquid cooling and a 560mm radiator (cooling CPU, motherboard, and GPU), which is a bit unusual for a workstation. When looking at Threadripper, even with my cooling solution, it would not be enough to meet this requirement. Fortunately I have better room cooling now, but this also means more power used when nobody is in the room.
It just seems like AMD should have some workstation boards using either their server CPUs or something more similar to their server line than the Threadrippers. The Threadripper line comes up short in all of these categories compared to the server line. However there are no workstation boards handling a CPU optimized for these workstation style demands.