I've never considered catching them all to be the point of the game - it's just a sort of side goal to strive for if you want. The point, IMO, is simply to make my way through the pokemon world - to catch, use, train and evolve pokemon to help out through the sort of dual quest of working up through the trainer ranks and eventually challenging and defeating the E4 and the Champion, and stopping whatever nefarious plan is being attempted by whatever organization pops its sinister head up. Catching lots of pokemon helps on that, since it gives me the chance to try lots of things out and see what's good at what and to hopefully work out an especially good team and set of strategies for accomplishing those twin goals, but that's about it.
That said though, the habitat list in BW2 has led me to be a lot more conscious of the possibility of catching them all. It's still not "all" in the dex sense, since it's only the ones that can be caught in the wild, but just the fact that everything that can be caught in the wild is listed in convenient subgroups by route and such, with easy-to-recognize markers for keeping track of what I've already seen or caught and of which routes I've completed and which ones I still need things from, has led me to go out of my way to make sure that I complete each of those lists. I guess that's a form of catching them all, though not the extreme (and at this point pretty much impossible anyway) version that's more commonly associated with the phrase. It's still nothing close to the "point" of the game as far as I'm concerned though, but it is at least a more significant part of it than it was to me before the habitat list.
