And apart from oxygen, there is no water on the moon either (at least, free, meteoric-derived water in liquid or vapour form) - which is useful in non-bacterial degradation processes.
I am not an Apollo astronaut, but I have held "moon rocks" in my hand and looked at them under a microscope [in thin section under polarised light for those that are interested]
They basically had the same composition (plagioclase, pyroxene and olivine) as fresh basalts here on Earth (although some samples were rich in titanium), yet these Lunar basalts were a bit older - by about 4 billion years.
It is the lack of weathering - requiring oxygen and water and a 'weather' system that kept these basalts as fresh as the day they were erupted.
Sadly, we weren't allowed to examine the samples labelled;
"Blue-veined Lunar Rock Sample - GZ25.3 - Gorgonzola - TOP SECRET"
or even the one labelled;
"CLASSIFIED - LUNAR SAMPLE CODENAME CHEDDAR"