You and me, are both right.
Practice rooms are good for several reasons, what both you and also @Liq and others mentioned. Maybe we will get some people coming back to the game and enjoying quick practice battles, but chances are we might loose people too, less people playing the "actual" game with already low number of players could also make people quit out of boredom.
Right now some players who are after "quick" action just grab a cheap ship and hit patrol zone just to fire some guns, those will probably just hit practice room instead and do the fighting there.
My advise is don't introduce practice rooms as an alternative to playing the actual game, instead make it so there is no need for practice rooms.
@Liq mentioned practice rooms good for people who just want to log on and have a quick fight.
Do we need practice rooms for that?, why?, because low population. Solution is not practice rooms, solution is to fix the population.
Aim for interaction, not segregation, unite instead of divide.