Does anybody out there use Authentication Header (AH)?

Hi, I am trying to see if there are people who use AH specially since RFC 4301 has a MAY for AH and a MUST for ESP-NULL. While operators may not care about a MAY or a MUST in an RFC, but the IETF protocols and vendors do. So all protocols that require IPsec for authentication implicitly have a MAY for AH and a MUST for ESP-NULL. Given that there is hardly a difference between the two, I am trying to understand the scenarios where people might want to use AH? OR is it that people dont care and just use what their vendors provide them? Regards, John