Because language is always political. Pronouns reawaken. Remember tis/ter/tem? A statement from Manjoo, a commentary from Language Log, and an index to earlier columns.
Manjoo is apparently suggesting that everyone should choose the opt-out option, at least with respect to pronoun choices, so that they replaces he and she just as you replaced thou. This will certainly get pushback from traditionalists like Mary Norris. Will there also be objections from people on the other side, who want to see explicit non-gendered pronoun choice retained as an expression of personal identity?