Or why I prefer "it" to the singular "they" for myself.
It seems to me that discussions of the use of singular "they" as a gender-neutral third-person singular pronoun always focus on whether or not it's grammatical. However, at least for me, this misses the point. Whether it's grammatically acceptable (I think it is, but I don't want to argue that here) or not, the way people primarily use it is not consistent with the pronoun I want used for me.
Consider the example sentences that come to mind of times when people use it:
"Someone left their coat on this chair."
"A good teacher should know how to encourage their students."
"Their name is Sam Smith."
In the first case, it's being used for a specific person, but one whose identity, and so gender, is unknown.
In the second case, it's being used for a generic entity that could describe many different people, who presumably have different genders.
In the third case, it's being used for a specific person whose identity is known, but whose gender isn't. However, this doesn't indicate that the speaker expects anything other than that they have a standard, binary, gender.
In other words, the singular "they" is a gender-unspecific pronoun. It--or your preferred alternative to it--solves the very real problem of how to refer to a person whose gender isn't known, or to a generic entity that might describe various people of different genders.
However, this also means that it isn't an appropriate pronoun for me. My gender isn't unknown--at least not to me, or to someone I'm telling what pronoun to use for me--and it's not changing. It's explicitly neuter, so "it" is a better pronoun for me. Even if people want to object that "it" is explicitly inanimate and that the singular "they" is ungrammatical, though, it seems to me that we do need two separate pronouns for these things.



