Because all the king's horses and all the king's men can't put the sample back together again

They are making more samples (bigger ones to test resistance).

My guess is that they already broke it to pieces and this one levitates slightly. Until they get more samples they will keep this one intact.

I think they didn't show that yet because for scientists, what they did already proves diamagnetism: they show that both sides of the magnet lift the sample.

They could more or less easily demonstrate levitation even with the current sample, by using four (maybe slightly stronger) magnets. Four magnets are needed so that the sample doesn't float to the side. Typically four magnets are used to demonstrate diamagnetism of e.g. pyrolytic carbon, see the picture in https://en.wikipedia.org/wiki/Diamagnetism

So in summary, they don't show levitation because that's scientifically not needed. It would be much more impressive for the non-scientist however, so I guess eventually they will show this. I assume another reason they didn't do that so far is that they are afraid to lose the tiny sample :-)

If you have four magnets all stuck together, the magnetic field is the same as if you have one large magnet.

Not if 2 magnets are flipped. Over just one magnet, the pyrolytic carbon (or LK-99) would slide off to the side. Over 4 magnets arranged correctly, it stays in the middle. This is described here: https://www.imagesco.com/magnetism/graphite-levitation-kit.h...

Some superconductors will float and stay over just one magnet, but it's a different story: https://en.wikipedia.org/wiki/Flux_pinning - LK-99 is not of this type as far as I know.

Already met the replication requirements.