Location and date of photos gets lost after being exported to external hard drive

So, you didn't export, you dragged and dropped? That's not really supported as a transfer method in Photos. You can do it, but what you get seems to change from version to version. As far as I can see, it's not mentioned in Apple's support documents. It works for, say, sticking a picture into a text or an email, but you can't depend on dragging and dropping for backups or anything really important.

The best bet is to use File>Export to export pictures from Photos. That way, you know what you get.

I'm not sure what you're doing. I just exported a picture from Mac Photos using File>Export nn Photos, and when I look at the Finder Info window it has the latitude and longitude, the title, and keywords as well as shutter speed and such. These also show up when I open them in the app GraphicConverter. The two places I exported to were Apple formatted. In Export I checked the the "Include" things. I'm using Ventura.

How is what you're doing different than what I did?

In Ventura, dragging from Photos to Finder seems to bring the full sized edited image, but with no IPTC info. It has Exif metadata, including GPS, but not keywords, title, caption, etc. Finder Info shows GPS, but not keywords, etc.

However, when I dragged a picture into GraphicConverter, it had not IPTC and it did not have GPS. Perhaps that is stripped when dragging into apps.

When I drag a picture into Preview, it is a "preview" image, about screen size rather than full sized.

Curious. Again, though, you just can't count on drag and drop...

I long since gave up on drag and drop for anything important. It started back in iPhoto and what you get varies from version it version of it and now Photos. The preview image is meant to be for easy sharing, to save you the bother of exporting. So, you get a medium quality version of your image with a (haphazard) selection of the metadata. Not important if you're sharing the image to a Pages document or sending an email to GrandMa with a snap of the kids. If your need is more critical than that use Export.

Drag and drop gets the preview of the image. File -> Export gets better quality