Read receipts

So my SO usually has read receipts on for me, but it seems like at some point during the night sometimes they get turned off. Whenever he notices, he seems to turn them back on for me.

Could this be a sign he is deleting our text thread? As in, worried someone will go through his phone at night? Because when you delete a thread the read receipts turn off and you have to manually turn them back on for that contact if you don’t have them turned on for all contacts. I could be over thinking it