1. because the site is a 3D accumulation, you need to remove layers to access what's below
2. to apply laboratory tech, you're not going to bring an electron microscope or an NMR spectrometer down a pit
3. to keep the artefacts from spoiling further
4. because spoilage of the artefacts will speed up once they're uncovered and exposed to the elements
5. to avoid thefts and secreting of the artefacts in private collections
6. because the state would have to confiscate all dig sites rather than temporary make them off-limits, which people already react to quite badly (especially when the dig site is a construction site which is rather common, look up "rescue archaeology")
The artifacts left in the ground will be around longer than the one put through your laboratory. The one left in the ground will be around for thousands of years. The one brought into your lab will be around for hundreds of years or less.
What you say is only so certain. You dont seem as quick to innovate as others. Why not put a building on top of it and add to its shelter? Everyone will react poorly to eminent domain. So what? Think about the variables.
We'll also know a lot less about them. What's the point of finding them and leaving them in the ground? You might as well not look for them in the first place.
You need physical access to the items to perform tests on them to understand where they come from and what they're made of. You also fund the further study of these objects by renting/selling pieces of the collection to museums, curators, and collectors.
2. to apply laboratory tech, you're not going to bring an electron microscope or an NMR spectrometer down a pit
3. to keep the artefacts from spoiling further
4. because spoilage of the artefacts will speed up once they're uncovered and exposed to the elements
5. to avoid thefts and secreting of the artefacts in private collections
6. because the state would have to confiscate all dig sites rather than temporary make them off-limits, which people already react to quite badly (especially when the dig site is a construction site which is rather common, look up "rescue archaeology")