Technically the Part 91 operators are required to respond with what they have for records, as it's mandated by an act of congress. However, Part 91 operators aren't required to keep the same records, generally, that 121, 125, or 135 operators must, and can't be expected to provide the same level of information.
The Advisory Circular and other information previously given allows additional details and exemptions regarding who must respond, with what, and how.
Whether a Part 91 operator responds or not isn't predicated on any benefit the operator may receive; it's predicated on being an aviation employer "person" as required to respond to record requests under the prior records improvement act. Not all are required to do so; exceptions and special circumstances apply.