Most of the episodes aired before at-home VHS was common, and TV stations weren’t in the habit of archiving their old footage for nightly broadcasts; The show was viewed as transient since it dealt with current events, and nobody expected people to want to re-watch old episodes. It’s likely that a lot of them aren’t available simply because nobody (including the tv station) has recordings.
Most of the episodes aired before at-home VHS was common, and TV stations weren’t in the habit of archiving their old footage for nightly broadcasts; The show was viewed as transient since it dealt with current events, and nobody expected people to want to re-watch old episodes. It’s likely that a lot of them aren’t available simply because nobody (including the tv station) has recordings.