Its kind of more interesting because you can find out more about whats happening 'under the hood'. When two people play its just 'clever brain vs clever brain' with no engineering details. When two AIs play you can say its this many racks of servers and teraflops and the other one has a model thats trained itself from scratch for a few hours or whatever and so when one of them starts to trample the AI opposition we actually learn something other than 'this person has a brain thats good at chess'.

e.g. https://www.bbc.co.uk/news/technology-42251535