They are likely looking for some activity that might lead to your payment of the debt, or they are merely atttempting to get your attention and remind you that the debt remains unpaid.
Neither credit report exclusion nor expiration of SOL discharges the debt. It is still a legit delinquent debt.
Situations can arise where a consumer is still required or has incentive to pay a debt that has become excluded from their credit report or is outside of SOL, such as when the consumer is applying for a large loan, such as a mortgage, where a prospective lendor requests a listing of all unpaid, delinquent debt. Remind you that the debt remains unpaid is a tactic to remind you of your potential disclosure obligation regarding the debt.
A consumer can send a debt collector a cease communication letter, thus barring any continued calls or letters, but cannot require a debt collector to cease and desist from otherwise pursuing legitimate business activities to attempt collection.
Out of curiousity:
Is there really much that can happen with a debt that has fallen off a report and can no longer be reported?
Granted, the OP's report has Midland snooping around, but if a lender sees a clean credit file, I would think that would be it. Especially with people that genuinely have bad memories and answer "I don't know" when asked about a collection inquiry (or however it shows).
In response to the question about excluded information being available to others, the credit report exclusion periods set forth under FCRA 605(a), including the exclusion of a charge-off or collection after no later than 7 years plus 180 days from the DOFD, are not absolute.
FCRA 605(b) exempts all of the exclusion provisions of 605(a) under certain conditions, such as when a creditor is requesting a credit report based on a consumer-initiated request for credit in an amount of $150K or more. The creditor can then receive a full factual credit report that includes any and all derogs that have become excluded under the normal exclusion provisions of section 605(a).
While creditors rarely request such full factual reports, the point is that credit report exclusion does not delete the derogs from the consumer's credit file, and under certain conditions, the derogs can still be included in a special credit report.