Its one thing to add $0.5 supercap and a diode to SSD (and still the likes of OCZ didnt bother for cost reasons). Its entirely another to slap bank of boost/buck converters, 100F cap and spider web of control circuity all over the place.

Adding $20-50 in bom the size of two D batteries just in case something _very rare_ happens is not economically viable. There are better alternatives, like banks of batteries ala google boxes. Turning server into oversized laptop gives you more than couple of seconds buffer.