Here is an irony, an atheist father and a Catholic mother had me baptized in a Lutheran Church as an infant as a compromise to get my Catholic Grandparents that never attended mass and Methodist Grandparents that attended regularly (every Easter and Christmas without fail) off their backs. The Protestants were adamant that I would not be baptized Catholic, and the Catholics were adamant that I would be baptized as an infant. The Lutheran Church was the only church that would meet the needs of the compromise. I was then promptly raised in the family tradition of religious lip service twice a year with no real belief that it was anything more than a social obligation ... like Jury Duty.
So I don’t think that a baptism of a faithless infant by two faithless parents followed by an atheist upbringing is really what anyone believes that the Bible had in mind. The irony is that God still claimed me, transformed my, indwellt me, and utterly saved me without any adult baptism. It was only 15 years later that I was at church watching a baptism ceremony at the Church of God of Anderson Indiana, that I mentioned in passing that because I was saved outside of any normal Church (it was a Catholic Charismatic Fellowship of laypeople that shared the gospel with a gang member), I never happened to get baptized. They viewed it as a much bigger deal than I did, so I agreed to be baptized as an adult. It sort of made sense given the gross insincerity of my infant baptism.
Anyway, when I later studied the meaning of Baptism with a Southern Baptist Convention Church, the memory of the event and the meaning of the event added extra impact and personalization to many verses in scripture for me. When scripture talks about how we have been buried with Christ, I can remember the water closing over my face as I plunged into the water. When it talks about washing away our sin, I can remember the feel of the water that washed away my sin. The Church of God used a Baptismal Pool (as does the Pentecostal Church I currently attend), but a part of me wishes that they had used “living water” ... a moving stream or river to more perfectly allow us to visualize the water carrying away our sins. When scripture talks about how we arise a new creation, I can remember the exhilaration as I emerged from the water. God had promised that I was now a new creation, and I felt like a new creation. It actually FELT like a rebirth as a new person.
That is why baptizing infants makes ME (personally) sad. I get that something to mark their admission into the Covenant is a good idea. Good enough that Credobaptists often have “baby dedications”. However you have created a wonderful memory for the parents and the grandparents, by stealing that memory from the child. He or she can never know the feeling that I felt and read those scriptures with the memories that I can apply to them. That makes me sad.
Welcome to seeing how sausage is made.

The Southern Baptist Convention is something like a group of little old men and little old ladies, 80% are always arguing about SOMETHING unimportant while 20% are getting all of the important work done. So the SBC tracks baptisms (I guess they think it is an important metric of something) and they track them by broad age groups. For a very long time, the youngest group was “Pre school aged” or “age 6 and under” with the next group being something like “7 to 12” and then “teens” that general idea. (I may be off on the exact age breaks). Around 2014 there was an uproar that the fastest growing segment for baptisms was the so-called “Dora Generation” (a clever name for children age 6 and under). The data was about 4000 children age 6 and under were being baptized per year (out of something like 15 million members). Remember those 80% that like to worry about unimportant things, well some of them started complaining that 6 and under was too young. The SBC did what any good bureaucracy would do, they stopped counting children age 6 and under. They simply rolled them into the next age group. So the latest data has the youngest group as “children age 12 and under”.
I suspect that the majority of 6 and under were age 6 with a few age 5. They just don’t keep that detailed of records on exact age and it is probably deliberate, so those are just my wild guesses.
Why not age 1?
If the Elders of a Baptist Church were convinced that a 1 year old had genuine faith in Jesus as their Savior, they would baptize them. I doubt that any Elder is comfortable with the evidence of belief presented by a 1 year old. Apparently there are some elders that are convinced of the genuine faith of some age 6 and under, and some that are not.