Yes, so it was not an Oblivion Developers are lazy thing...
No, I'd still say it's a matter of lazy design, just that it's one with precedence in the setting, and that alone does not mean it was a good idea, because, at least for me, Morrowind's leg structure made them more interesting, because it made them feel like a unique race, distinct from the others in the setting, rather than just people in rubber suits, so while the Morrowind design was different from that in Daggerfall, it was a change for the better, and sequels are supposed to improve upon what already exists in the series, not slide backwards, so while Oblivion's design may have been closer to how things were in Arena and Daggerfall, it was not a welcome return. That sort of thing is only good if a previous game has already strayed from the desirable path the series should take, and a return to how things were would be considered an improvement.
Just because things were a certain way in previous games of the series does not mean that's the best way to do them. And besides, it's not like Oblivion's Khajiit and Argonians are exactly like the version in Daggerfall, in fact, the Khajiit are much closer to the Morrowind version, just with a more human like body structure.
And besides I doubt that, when Bethesda settled upon the design for Khajiit and Argonians in Oblivion, the first thing they considered was not that they should make them more like in Daggerfall, it was probably rather what would be easiest to do.
Though honestly, the lack of claws bother me even more than the feet, especially since there's absolutely no justification for it, it's purely a matter of lazy design.