-server latency time (click-send-receive-manag-render-manage-compress-send-receive) ever wondered why website dont pop up in realtime
-massive additional hardware needed to render the game (100+ realtime calculation on one machine are more power consuming then 100+ individual machines at home)
-data management neccessery, remote and in realtime for millions of users
-physical limitations of broadband internet connections (cables. nodes and and and)
-massive compression on one side requires massive realtime decompression on the other one.... ever tried to compress a 800/600 video in realtime...good luck!
-pricing, to be able to run the latest games on the rendercluster it needs to be updated frequently....somebody has to pay it
-privacy, monopolizm, data security, data management (what happens with my data), downtimes,......
chess, poker, scrabble, yes
more wont work....but i am happy if they can prove me wrong
cheers