And why would you change 30 gallons of water a week? The point of having a large volume and a cycled tank is precisely that water changes do not need to and should not be larger than 10-20%, and depending on how stablished the tank is, the amount of plants, etc, changes may not need to be on a weekly basis, but more on a monthly basis.
I can see why you would think that smaller, uncycled containers are preferable if you think large tanks require frequent total water changes, but that is simply not the case.
Nobody debates that keeping axolotls in very small volumes of water is entirely possible, but it implies a lot more work and for a hobbyist is just inpractical and unsightly (although clearly individual preferences vary).