I noticed that the Gospel readings for Year A during the Third, Fourth, and Fifth Sundays of Lent are always the ones for the scrutinies, but in Year B, you have the option of doing John’s Gospel of the scrutinies (which is preferred if the RCIA candidates are attending Mass), and then you have the option of doing Mark’s Gospel (if the RCIA candidates are not present). Same thing with Year C. You have the option of doing John’s Gospel of the scrutinies, and then you have the option of doing Luke’s Gospel. Why is there no option in Year A, but an option available in Years B & C?
The readings for year B and C have less dramatic power than the three assigned Scrutiny readings for year A. Also they are to be assimilated gradually.
I’m totally taking a guess here, but probably to compromise.
They probably decided to make Year A the year that had the readings for scrutinies (probably because it came first when they were doing the cycle), but also wanted to keep the 3 year cycle of readings.
So, since Year A was (likely) written with the intention of being used for the scrutinies, they also made it an option for Years B and C if the scrutinies were being done. But because we all like the 3 year cycle of readings, when there’s no scrutinies we don’t read them so that we stay on cycle.
There’s no option in Year A because the readings for the scrutinies naturally fall during that time for Year A as part of the 3 year cycle, so you should be reading them anyways (because we like the 3 year cycle).
The Cycle A readings for the Scrutinies are rich is baptismal imagery. Today was water, next week is light, and the following week is life. That is why it is encouraged that they be used during cycles B and C as well.