I can't deny you make a very good point. And when you look at it from that prespective, I can't really argue.

But that leaves me with the question, why not just give us Doki in the first place?

Because we didn't get their Mario 2, but Nintendo still wanted us to get one. Why they chose Doki Doki Panic, I have no idea. Rather odd choice, for sure. But it probably has something to do with Doki being Nintendo's game from the start. It was probably the best option they had under their own roof.

As a side-note, I enjoy both Mario 2 titles, both the US and Japanese one. I played NES Lost Levels more recently, so it's more fresh on my mind. The reason I liked it is because of the interesting (and frustrating) level designs. The original Super Mario is kinda not as interesting by comparison. It was definately a worthwhile VC download for me.