Hydraulic systems are themselves complex and require many components all of which may fail. Detecting failure in a hydraulic system requires additional systems and is generally only indicative of overall system state rather than specific failure in a specific sub-assembly, on account of the shared nature of the medium. Assembly and testing are expensive.
Electronic systems are much simpler by part count, lighter, and smaller.
When communication fails, you know it's failed, and you know where it's failed.
Adding sensors for real time feedback is extremely cost-efficient. If your current/torque/temperature are not within an expected profile, a braking system failure may be inferred. This is extremely cheap, reliable and fast on low-end hardware.
In this case, they do not need left and right forms, they can just produce one part. Right away that's a huge saving in mold cutting time, mold storage, part production, distribution, etc.
In a mechanical system, if something fails, you have to disassemble the subsystem, identify the failure, search the supply chain for the part in question (possibly not labeled), obtain or manufacture the part, re-install it, and then hope for the best.
In a digital system, it can probably tell you what fails. It's probably cheap. It probably has the part number printed on it. And it certainly knows how many hours it has been used, and how heavily.
About latency, the key point is that humans suck. There's no way 1ms latency is going to alter driving outcomes. If you care about latency, you're autonomous driving. And that's something that electronics excel at versus humans. Let's say signals begin to come in suggestive of brake failure on one of four brakes while rounding a corner at high speed. ABS systems can compensate for the failure in real time and intervene to guarantee safety, even across subsystems such as by reducing speed. Mechanical systems are subsystem-bound and will leave the driver to 'discover' the 'new handling characteristics' at the point when it's already too late.
So the summary is: cheaper to produce, cheaper to assemble, cheaper to debug, cheaper to maintain, cheaper to replace, less unique parts, more freely positioned within a vehicle design, more readily reusable across vehicle designs, safer in some conditions, more suited to forward-looking applications such as autonomous driving.
(Disclaimer: I am not a mechanic, however I do have a fairly solid understanding of multi-disciplinary mechatronic design problems.)
As an aside, although we have no ongoing connection, I would note from experience some years back that Bosch VC have been one of the most stand out professional venture firms I have spoken to. If you have an industrial project, particularly one that connects with their existing business lines, they will not waste your time in providing a well considered and efficient response. Definitely a class act.