Brake fluid absorbs water and can corrode the cylinder which will play havoc with the seals which need to travel a lot further in the bore compared to a brake cylinder plus it gets used a lot more. It's very rare for a brake cylinder to leak and the more pressure you apply just drives the seals harder against the cylinder. I've seen more than a few clutch cylinders leak especially the slave which is usually in a dirty and wet environment....then you gotta periodically bleed them and make sure the reservoir is topped off.
Not saying hydraulic clutch systems are bad. The vast majority of cars are equipped with them but that is more likely due to cable routing and perhaps a smidgeon of not wanting to use "old school" technology in a modern car. Cables are just a stone cold simple and reliable method of getting the same job done and the pedal feel between the two is almost imperceptible.
