Vending machines outside is pretty much the standard for ramen restaurants. Most of them will take passmo/suica, which most foreigners are also likely to have since it is also used for all public transport.
I’ve been to this restaurant. They take cash as payment so I don’t think they are trying to dissuade tourists.
Also, just a short few years ago I would say less than 10% of restaurants took any form of electronic payment.
I've been 10 years on-and-off, and 10% sound way too low _if we include_ Suica/Pasmo. Credit card is another story and I'd agree.
This is also tied to labor availability. A vending machine interface is expensive to set up, but less than the cost of a full time cashier.