You might think that JR East has installed Suica gates in every station but this is not the case: as of 2018 Suica is installed in roughly half of JR East’s 1667 stations. One reason is cost. Unmanned stations have simple Suica gate readers but the cost of hard wiring these to the Suica data center is an expensive obstacle. Fast local processing is one of the advantages of Suica but the dedicated network backbone costs for linking and syncing with JR East servers doesn’t come cheap.
JR East is fixing the cost problem by developing a new cloud based Suica gate reader that can easily be installed anywhere. The trade off is slightly slower speeds, perhaps, with the benefit of lower installation and maintenance costs. JR East CEO Yuji Fukusawa says they expect to reach 100% Suica deployment with the new lower cost version during the 2021 fiscal year (also Suica 2 in 1 launch year) and hope to sell it internationally.
UPDATE 2021-04-06: JR East finally announced cloud based simplified Suica and extended coverage for the Tohoku region going online with 44 stations in early 2023, around the same time that Mobile ICOCA launches. This same cloud system is expected to drive JR East closed loop ticketing and more mobile based services in the future.