why does the macOS Recovery consistently fail??

Don’t understand how to successfully use macOS Recovery. Have a couple of old macbook pro’s I want to recycle back to Apple one day soon… Started with the oldest of the group, one from 2011 that still has a spinning HD.  We copied any desired files and then used Disk Utility to erase the disk using a low level of “secure delete”.  Took all afternoon…  

I could stop at that point but chose to try to see if I could learn how to use macOS Recovery (never used it before).  Used the power button to hard shutdown the computer.  Then restarted holding down <command> <R>..  It came up to an expected place where I saw 4 options, including Disk Utility and also “Reinstall macOS”.  Looking at Disk Utility contents, yes, I see a basically clean Macintosh HD and I also see a Disk Image called “OS X Base System”.  After looking at that, I go back to the four options (I don’t use Time Machine and never have, I backup a different way) and I chose “Reinstall macOS” followed by <continue>… That puts up a splash screen for macOS Sierra.  Before cleaning the hard drive, the computer had been loaded with macOS 10.12.6…. And that appears to be (what Sierra (10.12) was so that makes sense so far, that it would have a copy of Sierra saved on some Recovery partition…. Another <continue>….   It says next that it “needs to verify the computer’s eligibility with Apple”…. Have no idea what that could mean as it is not connected to any network anymore???  But though that step failed a couple of times, on several more tries, it has worked and proceeded on, whatever that means?? Then I had to agree to the license agreement…. Agree and then onward…   It offers two possible install locations, the Recovery HD that is grayed out so not really a choice (says it is 650 MB total with 66 MB available)…. And the other choice is “Macintosh HD” with 750 GBytes available…. I make the one obvious choice and click “Install”…

Then comes the frustrating part…. It says it will take 6 minutes…. I watch it count down (5… 4… 2… 1… 30 seconds… ) until it appears to get done…. I’ve seen it count down to where it says 0 seconds remaining…. I’ve also seen it report the bogus (and repeated more than once) “-399 seconds remaining”…. But even when it came down to 0 seconds remaining, it just sits there forever, NEVER offering any other button other than “cancel”…. 

Then there’s the “installer log” which puts up all sorts of error related stuff that likely would tell me, if I understood what it meant” why it can’t succeed…. 

I have pictures of the “installer log” and so forth but not sure any of that would be very helpful…. Any input on why I cannot successfully install a new copy of macOS Sierra (10.12) on this soon to be recycled computer???  thanks...