Tooling and support. You don't really want to mess around with a RISC-V softcore, you just want it to work and interface with the stuff you actually care about

Tooling and support. You don't really want to mess around with a RISC-V softcore, you just want it to work and interface with the stuff you actually care about already. MicroBlaze allows you to literally construct your own softcore via drag-and-drop, selecting from a wide variety of configuration options and peripherals. It includes SDKs for your custom applications, and debugging tools to figure out what's going wrong. I would not be surprised if development using SERV would take several orders of magnitude longer, solely due to immature tooling.