We've been using the lattice modifier to make the tire rounder. Could it be used also to inflate the tire's sides, or is there a specific reason for us to do that by moving the edges around?
Yes you can use it for that, maybe you will need to make more cuts to the lattice to have more wiggle room. Try it out, experiment a bit, you'll like it. In Blender there is so many ways to skin a cat, there's more efficient and less efficient ways, but hardly any can be considered wrong, if it gets the job done it's mostly fine.
Pretty much echoing what Omar has already said! The lattice is a great way to non-destructively manipulate the geometry without having to edit the underlying vertices. This could be a great way to inflate the sides of the tire as well, keeping in mind that you may need some more slices on your lattice for more granular results.
To the second part of your question, the main reason I went with modeling out the sides of the tire in our base mesh was because it allowed us to easily model in features to the sides of the tire, such as that circular cut that we do into the Tractor Tire episode. This is an area that may be harder to achieve by using the lattice, thus why I opted for something more manual. The lattice would start to get overly complex if we wanted to start adding designs or patterns into the side of the tire that actually cut inwards on the tire.
Ultimately it's a game of trade-offs when working in 3D. For me, the lattice was a great option to easily push out the silhouette of the tire but would've quickly over-complicated those other design aspects. :)
Understood, thank you for the explanations!
I will try to remake the tire using the lattice for the sides too once I'll be done with the whole tutorial, so to see by myself the ways in which the lattice makes things more complicated for certain steps. I think it should make it easier to get a better feel of the modifier and help in the decision if to use it or not in future projects!