cthrall, Thank you for posting in the Intel® Communities Support.
In reference to your question, the main reason why the Intel® Core™ i9-7900X was discontinued is due to market demand.
Just to let you know, even though the Processor is no longer manufactured we still provide technical support for it. Attached to this post you will find a PDF file with further details about the unit.
Any questions, please let me know.
Intel Customer Support Technician