According to Rashi, this indicates that entry to the sanctuary must be limited to the right people at the right time and in the right way.
There is a Chassidic explanation that is not literal in the way it reads the Biblical text but still conveys a worthwhile lesson. It says that “coming near to the sanctuary” in the sense of coming to the synagogue must not be left to great occasions like Shabbat and the festivals but must become a daily habit of the ordinary person.
Because this has not yet become the general rule, there are still synagogues where when someone who is not a regular comes to a service, they are immediately asked, “Do you have Yahrzeit?” It is rather unusual for the answer to be, “No – I just fancied coming today!”
Why people should chose to come to a weekday service is presumably because they want to pray with a minyan. There is a social dimension of the weekday congregation that also ought to be acknowledged.
The minyan is a chevrah, a fellowship where one has a feeling of belonging. In the minyan people have a bond with each other that involves their differences and their commonalities. It may not be the right word to use, but the daily minyan is one’s club.
Friends meet there and begin the day with a nice feeling. If someone does not turn up because they are ill, the others feel the pain. If one of the regulars has Yahrzeit, they all wish him long life and he wishes them the same.
The world outside is full of pressures and plagues; in the minyan there is warmth and security.