Vertical farming would be great for us on Earth because we are running out of space to grow food, but in a Galaxy with tons of planets for space, this would be unnecessary, correct?
The answer to any question of "should we do X" can always be rephrased as "is the benefit of doing X greater than the cost(s) of doing X". So let's rephrase:
In a civilisation that has access to tonnes of planets, would vertical farming outweigh the cost of setting up the farms?
For certain planets, the answer would be yes. Temperate planets that are close to existing hub worlds for example would have low cost of transport for goods manufactured on them (food included), thus more extreme forms of manufacturing (such as vertical farms) could be utilised before it becomes inefficient to build more dense and/or complex systems.
It's not just a matter of the space required, but also the world's climate (and how easily it can be terraformed), as well as how it relates to the economy at large. If it is in a convenient location, or is highly abundant in a particular resource, then it may be worth it to employ advanced engineering techniques to maximise the utility of that planet.