The short answer is
Because MediaTek's MRE platform never received official development support from WhatsApp, a native .vxp version was never created. How Users Attempted to Run WhatsApp on VXP Devices whatsapp vxp
While various websites claim to offer a "WhatsApp VXP" download, there is currently for the VXP/MRE platform. vxp Whatsapp - Facebook The short answer is Because MediaTek's MRE platform
Implementation considerations