Costs.
I just want a steady sustained progress in space exploration and colonization.
I don't like stops and starts, gimmicks like "firsts in space", and starting over from scratch.
But worst of all spending billions of dollars on R&D only to get nothing.
If we can't afford a Low Earth orbit space station, and there is talk of not even completing it, how are we going to afford a Moon base or better yet supply or rotate crews on Mars?
I believe our machines will go and prepare the way for us long before humans go anywhere to stay.