the question comes up from time to time.
the reasons vary from topic to topic.
as one example, there are a lot of locked topics right now because so many people are posting here about missing pictures instead of consulting and following the contact information and instructions clearly posted at the top of Main.
somebody finally provided the information the techs needed to start investigating. now, there are some instructions members can try. they're posted at the top of Main.
i added a link to all of the topics i encountered and then locked them.
had members been able to add comments, that information would have gotten lost and forgotten because so many people don't take the time to read through a topic before they add their two cents. those topics are locked to prevent them being taken off-track.