Worth it to Link Reservations
 

We are a family group of 7 and have TATL tickets one three separate locator codes. Should we ask Delta that the be linked?

Yes. Mainly b/c it can't hurt. But also in case of IRROPS they supposedly work to keep you altogether. Sometimes it happens. Sometimes not. There's no other real benefit as far as I know.

It just takes one IRROPS group break up and you will always link after that!

Worth it? Absolutely.
Guarantees you'll all travel together? Should help, but no guarantee. It's an advisory only.
(Btw, one good reason to travel on split PNRs. Upgrades to a PNR with one or two may be possible. On a PNR with 7? Unlikely.)

DL does not "link" tickets. All it does is place a manual reference to the other tickets in the PNR notes. In the unlikely event that there a human being looks at the PNR notes, it might be useful. If you misconnect or have other IRRROPS, presumably you are on the phone or standing in front of an agent and can mention all of this. If this is an auto-rebook, the system won't "read" the PNR notes. On the other hand, "linking" does not affect upgrades or anything else either/

I guess ultimately what I am hearing is "hey it don't hurt" (do no harm) so why not if you have the time, simply call and do it. But don't expect it to magically fix/guarantee you won't be split, etc

I don't know if it's coincidental or not but whenever I travel with companions who are non-elite, infrequent flyers on PNRs linked with mine, everyone gets "my" TSA PreCheck.

Definitely link them. It's particularly helpful when there's a problem and you can't pull up all the confirmation numbers up because of some issue (slow internet, phone not charged, papers in the overhead bin while you are on an active taxiway as your misconnection is happening).

Unless you want to purposefully lose a few family members.....