Why would he only text and never call?

I met a guy online and we kinda hit it off. We've been talking for over 3 months and we only text. We don't talk dirty so I know he isn't a creep and hopefully not a scammer cause I've seen his resume and we discuss his work at times. I know what we have is very casual but I believe a phone call is more effective way of communication than a text. He never brings it up and brushes it off when I try to suggest if we should call. I'm thinking of ending this cause , I feel he's not too interested and I'm not satisfied with text based conversations. Any suggestions?
Why would he only text and never call?
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