From Wikipedia:
Public utility: A public utility company (usually just utility) is an organization that maintains the infrastructure for a public service
Public service: A public service is any service intended to address specific needs pertaining to the aggregate members of a community.
Major oil&gas infrastructure almost never serves “aggregate members of a community”, it serves other companies or the community itself.
To be clear, I am not talking about street cabinets with some gas meters. These can and should be tagged with utility=gas, no problem. But as soon as it is in the size range of a landuse, not anymore. Then, they’re usually industrial facilities and should be tagged as such. Other existing tags describe their function (pipeline=substation substation=compression for example)

Because it is wrong (or at least stretches the term “utility” veeeery far) and an industrial classification describes those features more accurately.

Okay, agree with the first point. But I don’t think this is a good solution you’re proposing. I mean, I ain’t got a better one, but I also think that this is a very low-importance problem.
The refinery example dosen’t confuses anything, because a refinery always processes crude oil into petroleum products.

What are those industrial perimeters, other than (waste)water plants? Do you mean some kind of inspection stations or pump stations or something? (i’m not familiar with this)

Because man_made=works are manufacturing companies. Waterworks/wastewater plants don’t fall into this category.

So that to get such broad data you only have to utilize one instead of -lets say- 5 different keys? To have tags on hundreds of thousands of objects, which are actually obligatory and of course also have to be maintained, is not proportionate.