Why do many of my apps not show the version number?

You can try opening the application, in the menu bar click the "applications name", then from that drop down menu click About "name" of application it should have the version there. Safari example shown here.

I opened Safari, Clicked on Safari in the menu bar, clicked About Safari.

I've not come access an application that this info is not in this location.

Update alerts should not be coming from emails, they should come when you launch an application, or better still usually under Help in the menu bar there is a check for updates.

You can also go to the developers site and check for updates, almost all have this feature. An update notification via email should be a red flag, don't click on it it, write down what the application is and what version you are supposed to update to, then check the version that you are running as explained above, or the developers site.

These emails could be some kind of phising/malware, or other nefarious thing . NEVER click on any POP-UP update.

Less a problem emanating from Apple, I think. I find similar shortcomings but some developers, om the other hand, are meticulous with their updates. I think it is down to the developer to notify and provide the update to Apple. Apple has no reason not to show them once advised.