your typical satellite modem will have an RF interface either somewhere between 70 to 140 MHz (where it's intended to be upconverted/downconverted by the LNB and BUC/SSPA at the antenna), or somewhere between 1100 to 1900 MHz, both intended for attachment to low loss coaxial cables. This works fine if you're putting the modem fairly close to the LNB and BUC/SSPA. If it needs to be a hundred meters away or something, it's a lot of RF loss, and path loss/link budgets in geostationary satellite are already hard enough without introducing any more loss at the ground side.
I would imagine it's because electrical amplifiers, filters, and other such items are cheap and well understood. Whereas optical amplifiers, filters, and other such things, particularly ones that operate at low-GHz frequencies are expensive and kinda wild
well, an optical amplifier wouldn't do anything at all attached to a waveguide into a feed horn, in something like a 6.3 meter ku or c band cassegrain antenna design antenna aimed at a geostationary satellite... that's the job for a BUC/SSPA. You need. it needs to be RF.
rf over fiber in a satellite teleport application is more about being able to separate the modem from the antenna-mounted LNB and BUC/SSPA which might be some distance away.
