You don't get carpenters that only use nails and others that only use screws. They use the right tool for the job.
In the same way its good to have a carpet rake, a carpet brush, a tampico carpet brush, a crb, a rotary etc etc. Each tool can be used to agitate in the most appropriate situation. for example a crb may not be the best thing to use on a loop pile wool carpet and a tampico brush will not be the best thing for carpet tiles.
The average carpet brush is the most versatile agitation tool there is though and can be used for most agitation tasks. (with enough elbow grease)