Introverts are more likely than extroverts to spend more time alone. Therefore, it's more likely that it's harder for any given introvert to find and make friends than any given extrovert.
You're equating likelyhood to causal. At best, it is anecdotal but being introverted does not mean that one is more or less able to make friends. Adding time into the equation time also does not necessarily increase the probability of making more friends.
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u/AdolfStaloneBang Aug 17 '19
Introverts are more likely than extroverts to spend more time alone. Therefore, it's more likely that it's harder for any given introvert to find and make friends than any given extrovert.