> Ukraine could also reach Moscow with missiles, why doesn't it?

Ukraine doesn't have enough missiles to reach and hit important targets in Moscow.

Due to Moscow having the best defence, it doesn't make sense to try to hit it only for lulz, instead of hitting actually important target elsewhere, like oil refineries.

Otherwise, Ukraine has constantly been trying to hit targets in Moscow and around it, mostly with long-range drones, not missiles. Sometimes this has been successful. I mean, the dome of the Kremlin itself was hit a few years back.