Having refresh rate clocks being set by the AC rate is a bad idea since even with modern power grids, there is still some deviation in the nominal 50 Hz for Europe and 60 Hz for the US. Even if it's just ± 2 Hz there may be undesired side-effects.
Of course, with LCDs, you no longer have that pulsed cathode ray but the CCFLs, even on DC, (cf. to CFLs on AC used for lin-room lightning) are oscillating (you can see this very "neatly" when they are broken and start flickering, just like your old 60 Hz CRT 
). This is a form of PWM used to dim the backlight. Unless you operate at 100% brightness (and maybe even then to optimise contrast and/or colour trueness on a factory-calibrated display) it will pulse with the rate being dependent on the brightness.
With LEDs, I suppose, it would be a similar as you cannot simply dim them like a bulb by reducing the Voltage. Of course, if they were to run on AC, being diodes, they'd flicker.
As Jeff's said, you either have to match the room illumination frequency exactly on that on the monitor or you'd have to use a freq that is different enough to prevent interference (cf. beat).
Of course, in the Ancient Times™ when illumination was done by bulbs and monitors and TVs were CRTs and had their flyback transformers were driven by the same frequency, that of the power grid.
Hence, even with variations in power supply, they'd correspond. There were no PLLs to generate clock, only coils and capacitors...
Naturally, it was wise to use a frame rate equal to that frequency, hence PAL with 50 Hz and NTSC with its 60 Hz (nowadays 59.94 Hz, whyever...)
Anyway, as to the advantage of 75 Hz to 60 Hz on an LCD, I'm not quite sure.
Naturally, higher freq means higher bandwidth but the question is, what gives...
One advantage may be a higher frame raten when running on V-Sync; that should result on smoother animations.
If you playback video material, synching to 75 Hz may even be more complicated and could result in tearing artifacts.
For browsing the web or word processing, I doubt it really matters.
Hence the question, why all this efford?
Usually, I do integrate/install monitor drivers if available but rather to have the supported resolutions and horizontal frequencies set up properly for the graphics driver.
Also, some contain ICCs which improves colour reproduction and calibrates them to sRBG colour space (much needed with most LCDs --> new, true white (not fake blue LEDs with yellow phosporous coating!) LED-powered backlights can sometimes even outdo CRTs in this field and cover even more than the Adobe colour space).
I'd rather be able to enforce per-pixel display on LCDs rather than have them bloat the image to full size, more often than desired not even respecting aspect rartio, resulting in a blurry, distorted image.
Yuck!
