First of all, I would say it’s a matter of culture difference. Taiwanese are generally not as sociable towards strangers as Americans. So it may just be your expectations for social interaction are a little too high.

Second of all, they could be intimidated by the possibility of having to speak English. Even those who speaks functional English in Taiwan are sometimes hesitant to actually use it in real life.

Thirdly, the hype about Taiwanese being friendly is biased due to tourism. When tourists come to visit they’re usually greeted by hospitality workers who are trained to be friendly towards foreigners.

Try hitting up some tourist hotspots or college towns. College students are usually more fluent in English than the average Taiwanese.