(1) On the mistaken belief that not using "I" will help students understand the difference between objective and subjective writing.
This approach doesn't work; instead, students begin to think that simply removing "I" makes something objective, which is nonsense.
(2) As a way to help students write claims: Alien abductions are false. Designated smoking areas are a good solution for on-campus smokers. Peter Falk is adorable.
I support this reason for excising "I" since being able to produce and defend claims is necessary to academic and business writing. The lawyer doesn't say, "I really, really, really hope my client is innocent." The lawyer says, "Bob is innocent" (claim). The inventor doesn't say to a room full of venture capitalists, "I think my invention will make lots of money. But hey, you can make up your own mind" (I literally beg my students: "PLEASE do not end your argument/persuasion paper by telling the readers that it is all just your opinion, and readers can make up their own minds. Of course they can! But after spending a whole paper arguing that a particular position is right, don't give it up at the end!")
(3) In the hopes that not using "I" will inspire students to make more general applications.
I agree with this reason to an extent. But it should be backed up by additional instruction. For example, far too many English instructors assign "a narrative" as an essay in its own right, not as evidence for a claim. I discuss narrative writing more in a later post. Suffice it to say here that far too many students think that writing for English means "I write about myself; then I write about myself; then I write about myself" without wondering, "Why would anyone care?"
(4) In an effort to force students to produce more formal, "business-like" writing.
"I"=informality is a debatable claim. In academic research writing, "I" is not entirely acceptable, but it has become more common, especially in the sciences (since passive voice--"the experiment was done by"--is way, way more annoying than active voice, even for scientists).
Using "I" is far more acceptable in business writing. At the law firm I worked at, the lawyers used first-person all the time to communicate with insurance adjusters, clients, and other lawyers. There is nothing more daft than supposing that a lawyer would write a summary and analysis of a deposition for an insurance company and NOT use first-person. The insurance company is paying the lawyer to find out what she thinks, not to produce some unnecessarily wordy document in passive voice (no matter how good the lawyer is at the latter!). Someone has to take responsibility for the recommended course of action!!
In general, when it comes to academic and business writing, the overuse of "you" bugs me more than "I".
Where do I support the use of "I"?
1. In an anecdote at the beginning of an essay. I also support the use of "you" here: You wake in a strange room. Your phone isn't working. From outside comes the sound of breaking glass. This may be the worst vacation ever.
2. In the evidence. If the writer is using primary "I was there and saw it happen!" evidence, first-person is obviously the best voice to use!!
3. At the beginning of the conclusion.
No "I" (or any variation thereof):
1. In all claims, including the thesis and topic sentences (the sentences that begin body paragraphs).
2. At the end of the conclusion. End on a big thought! Apply the essay to the reader! Don't assume the reader knows who you are! The essay should never be the equivalent of a home movie!