[Why use beams? Their heavy turbo lasers dish out a lot more damage than basic beams.
Range. Iirc most beams have a range of 1 to 2 clicks at least, whereas you generally see Star Wars capital ships closing the distance for broadsides and stuff. And since beams can pierce shields and deliver pinpoint damage, GTVA capital ships would be able to decapitate the bridge, or selectively damage sections of the ship, e.g engines. And in RoTS we see the clones reloading the heavy turbo lasers with "shells"(more likely to be a massive battery) while in FS2, the beams merely need a few seconds to recharge.
If the Hoth shield was strong enough to "repel any bombardment", why not the Lucifers?
The Lucifer ostensibly uses its beams for bombardment; if it uses its lasers as well, we need to remember that in the SWars universe, shields are used to deflect and block
lasers, while the default "lasers" in FS2 are actually
xasers which use X-Ray particles instead of focused light. This means that the laser weapons in FS2 would be able to eventually wear out the Hoth shield.