In any corporates network you see job requiring Cisco certificates. Those employees then choose to buy Cisco rather than something else, and the support deals require the companies to maintain the employees Cisco papers and training, often with free trips to conferences in luxury locations.
The engineers wouldn’t recommend another brand of router which may be better because they’d lose their perks and face difficulty moving to another job.
It’s a self sustaining industry.
No surprise Amazon want the same thing.