plants have a proven track record of scrubbing CO2 out of the air that goes back hundreds of millions of years. they are extremely reliable, and won't break down just because a part got worn out. they do not require that you carry extra parts, and they are also good at reclaiming other waste products. they additionally provide valuable resources including food, building materials, fabric, medicine, and even some recreational drugs.
if you're going to go someplace so far into deep space that a small-scale infinite power source is worth the investment described (and therefore are not within range to get any replacement parts for machines), then why would you use anything other than plants to keep your air supply clean?
(i can certainly understand wanting to have emergency backup systems to rapidly replenish air supplies, but for the long haul, it really just makes sense to use plants).
if you're going to go someplace so far into deep space that a small-scale infinite power source is worth the investment described (and therefore are not within range to get any replacement parts for machines), then why would you use anything other than plants to keep your air supply clean?
(i can certainly understand wanting to have emergency backup systems to rapidly replenish air supplies, but for the long haul, it really just makes sense to use plants).
It's a question of size required, which adds weight, which means more fuel required and a higher ship construction cost. For a ship that just does Earth to Mars round trips - maybe. Plants take time to produce food, and IIRC, a good yardstick is 1 acre of land per person per year to grow food. If you're transporting 100 people, do you really want to have to build a ship that has 100 acres of space inside? Investing in a permanent magic item enchanted with the Hibernate spell, or using an endless electricity item to power 2070's biostasis chambers both seem like way better ideas to me. A nice compact ship, with the passengers as cargo and the piloting computer doing the driving.
EDIT:
On the other hand, if I were building a Space Habitat, absolutely, bring in and grow as many plants as possible. Everywhere you can cram in another plant, do it. Not just for the physical benefits you've pointed out, but they also help provide as much of a manasphere as possible for the place.
This begs the question - just how much vegetation is required to equal Earth's manasphere? How much to compensate from -12 to 0? The Ares Eden space station is described as having an "anemic" manasphere, so what if we built one ten times that size? A hundred times bigger? A thousand times bigger? This discussion does raise some other interesting questions as well.