Ever notice that while the statues are are always old and crumbled, the power-ups that they hold are always nice and shiny, as if they were brand new?
Maybe they have some sort of repair system installed in them to keep their treasures in perfect condition instead of old and unusable?
Just a guess. I'm not a Metroid expert, so I wouldn't know squat from the series.
The Chozo boast some of the most advance technology in the galaxy, but they use traditional building techniques in their temples (stone and mortar, even vegetation) for no other reason than they like it that way. After thousands of years the stone edifices may crumble, but the virtually indestructible treasures within remain, along with their machines. Kind of like keeping a diamond in a display case made of glass and wood, after several hundred years the glass will shatter and the wood will rot, but the diamond is virtually indestructible and will be just fine.
Well, there is the occasional Torizo, I think they're called. You know, the Chozo Statues that get up and attack you? It'd be interesting if Samus' powersuit was being guarded by one.