Convince people you have an iPhone
By mentioning that you have an iPhone rather than just calling it a phone
E.g. "I was calling someone on my iPhone the other day." As opposed to just saying, "I was calling someone on my phone the other day."
No one else mentions what phone they have. "I was calling someone on my Samsung Galaxy S II the other day."

*this message was sent via iPhone*
(wehttamman via B3ta for microwave, Fri 27 Apr 2012, 21:33, 2 replies, latest was 13 years ago)

I think even
"on my phone" is redundant. People aren't going to assume you was calling someone using smoke signals if you neglect to mention the phone bit.
( sandettie light vessel automatic New Twitter - @bollocksreally, Mon 30 Apr 2012, 16:08, Reply)

True
But people still say it
(wehttamman via B3ta for microwave, Wed 2 May 2012, 0:57, Reply)